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Book of Abstracts
of the XVth International Feofilov Symposium
on Spectroscopy of Crystals Doped with
Rare Earth and Transition Metal Ions
Kazan – 2013
3
Organizers:
Kazan Federal University
RAS Council on Spectroscopy of Atoms and Molecules
E. K. Zavoisky Physical-Technical Institute RAS (Kazan)
A. F. Ioffe Physical-Technical Institute RAS (St.-Petersburg)
Organizing Committee Co-Chairmen:
Gafurov I. R. (Rector KFU, Kazan)
Kaplyanskii A. A. (Academician RAS, St.-Petersburg)
Members:
Aganov A. V. (KFU, Kazan)
Salikhov K. M. (Kazan Physical-Technical Institute)
Tagirov M. S. (KFU, Kazan)
Tayurskii D. A. (KFU, Kazan)
Tarasov V. F. (Kazan Physical-Technical Institute)
Local Organizing Committee
Nikitin S. I. (KFU, Kazan) – Chairman
Gafurov M. R.
Zverev D. G.
Volodina I. P.
Motygullin I. G.
Baibekov E. I.
Klekovkina V. V.
Symposium secretary
Yusupov R. V. (KFU, Kazan)
Programme Committee
Malkin B. Z. (KFU, Kazan) – Chairman
Eremin M. V. (KFU, Kazan)
Feofilov S. P. (Ioffe Physical Technical Institute, St.-Petersburg)
Moiseev S. A. (Kazan Physical Technical Institute)
Popova M. N. (Institute of Spectroscopy RAS, Troitsk)
Nikiforov A. E. (Ural Federal University, Ekaterinburg)
4
Sponsored by
Russian Foundation for Basic Research
Dynasty Foundation
Government of the Republic of Tatarstan
Bruker Ltd., Moscow
5
6
Symposium Programme
16 September 9.40
10.00 Symposium opening
General problems of spectroscopy
10.00
10.30
Mo-1
V. S. Zapasskii
Signals and Noise in Polarization Magneto-Optics
10.30
11.00
Mo-2
N. N. Rosanov
Parametric Doppler Effect in Nonlinear-Optical
Crystals and Dielectrics
11.00
11.30
Mo-3
F. Pelle
Beyond diffraction limit using upconversion
11.30
11.50 Coffee break
11.50
12.20
Mo-4
B. S. Tsukerblat
Symmetry Adapted Approach to the Dynamic Jahn-
Teller Problem: Advances and Challenges
12.20
12.50
Mo-5
V. V. Hizhnyakov
Optical Jahn-Teller effect in impurity centers of
crystals: contribution of phonons
12.50
13.20
Mo-6
M. N. Popova
Spectral signatures of random deformations in
crystals
13.20
13.40
Mo-7
V. V. Gudkov
Vibronic interaction in ZnSe:Cr in magnetic field
Lunch
Quantum memory in rare earth doped materials
15.00
15.30
Mo-8
B. S. Ham
Rephasing-based solid state quantum memory
15.30
16.00
Mo-9
R. Akhmedzhanov
Logic gates and storage elements based on ion
ensembles in a Pr3+
:LaF3 crystal
16.00
16.30
Mo-10
Ph. Goldner
Spin dynamics in rare earth doped crystals
16.30
16.50
Mo-11
N. Sinclair
Frequency-multiplexed quantum memories with read-
out on demand for quantum repeaters
16.50
17.10 Coffee break
17.10
17.40
Mo-12
S. A. Moiseev
Photon echo quantum memory with Raman atomic
transitions
17.40
18.00
Mo-13
A. Louchet-Chauvet
Stimulated photon echo and time-reversal of
optically carried signals
18.00
18.20
Mo-14
D. Serrano
Spectroscopic investigation of Y2SiO5 codoped with
Ce3+
-Pr3+
and Ce3+
-Eu3+
ions for potential quantum
computing applications
18.20
18.50
Mo-15
S. Sekatskii
Fluorescence Resonance Energy Transfer Scanning
Probe Microscope-controlled quantum computing
using optical transitions in rare-earth ions in crystals
19.00 Welcome party
7
17 September
Spectroscopy of transition metal
oxides
Spectroscopy of materials for
quantum electronics
9.30-
10.00
TuI-1 D. van der Marel
Optical properties of strain- and
composition tuned RNiO3
TuII-1 W. Strek
Broad band anti-Stokes emission in
Rare Earth systems
10.00
10.30
TuI-2 M. Grüninger
Orbitons and orbital correlations in
RVO3 studied by RIXS and optic
TuII-2 G. E. Malashkevich
Visualizer of UV images on the
huntite-like glasses co-doped with
Ce, Tb and Sb
10.30
11.00
TuI-3 A. S. Moskvin
Charge transfer transitions in optical
absorption and luminescence of NiO
TuII-3 H. R. Asatryan
Advances in Electron Paramagnetic
Resonance of Transition Elements
in Materials for Quantum Electronics
(YAG, YLuAG, YAP, YLuAP, ZnSe)
11.00
11.20
TuI-4 V. I. Sokolov
Temperature influence on the narrow
lines I1 and I2 in Ni0.6Zn0.4O X-ray
excited luminescence spectrum
TuII-4 M. Guzik
Spectroscopic properties of new cubic
tungstates doped with Eu3+
and Yb3+
ions
11.20
11.40 Coffee break
11.40
12.10
TuI-5 A. Boris
Electron-phonon Interaction in the
Hyperkagome Lattice Iridates
TuII-5 W. Ryba- Romanowski
Optical properties of crystals doped
with Sm3+
or Dy3+
relevant to potential
InGaN/GaN laser diode-pumped visible
laser operation: A comparative study.
12.10
12.40
TuI-6 G. Khaliullin
Magnetic order and excitations in
iridium oxides
TuII-6 I. N. Yassievich
Nonresonant excitation of Er3+
ions in
matrices containing Si nanocrystals
12.40
13.10
TuI-7 V. Kataev
SUB-THz spectroscopy of the
layered manganite LaSrMnO4 in
ultra-strong magnetic fields
TuII-7 M. E. Doroshenko
Spectroscopic and laser properties of
Zn(1-x)Mg(x)Se single crystals doped
with Fe2+
ions at room and low
temperature
13.10
13.30
TuI-8 I. R. Mukhamedshin
NMR/NQR evidence for charge and
orbital order of cobalt ions in NaxCoO2
TuII-8 E. B. Dunina
Influence of excited configurations on
intensity of electric dipole transitions of
rare-earth ions
Lunch
15.00
15.30
TuI-9 J. Deisenhofer
Low-lying excitations in the orbitally
active A-site spinels FeSc2S4, FeCr2O4,
and FeCr2S4
TuII-9 S. Zazubovich
Processes of energy migration and
transfer in Gd-rich rare-earth-doped
phosphates
15.30
16.00
TuI-10 K. Boldyrev
Specific electronic and vibronic
structures of cuprum metaborate
(CuB2O4) optical spectra
TuII-10 A. Belsky
Selective excitation of energy transfer
processes from host excitations to
doped ion in Li(Lu,Y)F4:Ce crystals
8
16.00
16.20
TuI-11 L. S. Kadyrov
Boson peak in overdoped manganites
La1-xCaxMnO3
TuII-11 G. Boulon
Research on rare earth-doped
sesquioxides elaborated by Spark
Plasma Sintering method
16.20
16.40
TuI-12 S.I. Nikitin
Mixed valence pair center Cr2+
-Cr3+
in
KZnF3 crystal. EPR and optical studies
TuII-12 A. Pogrebna
Magnetooptical time-resolved study of
Eu2+
spins dynamics in EuFe2(As1-xPx)2
pnictide superconductor
16.40
17.00 Coffee break
17.00
17.20
TuI-13 G. S. Shakurov
High-Frequency EPR of Fe3+
dimers in
α-Al2O3
TuII-13 S. A. Shnaidman
Pump-induced processes in Ce3+
:CaF2
crystals co-doped by Yb3+
and Lu3+
ions
17.20
17.40
TuI-14 R. V. Yusupov
Microstructure of the dynamic Mn2+
centres in SrTiO3: EPR and optical
studies
TuII-14 V. V. Pavlov
Photoconductivity and photodielectric
effect in LiY1-xLuxF4 crystals doped by
Ce3+
and Yb3+
ions
17.40
18.00
TuI-15 Yu. E. Kitaev
Manifestation of the intermediate
monoclinic phase in IR-and Raman
spectra of ferroelastic K3Na(CrO4)2:
MnO42-
crystals
TuII-15 K. N. Guliaeva
Cathodoluminescent study of energy
trap states in ceramics based on
YAG:Nd
18.00
18.20
TuI-16 E. S. Demidov
High-temperature diamondlike silicon-
based ferromagnetic with self-
organized superlattice distribution of
Mn impurity
TuII-16 V. G. Gorieva
LiY0.3Lu0.7F4: Ce3+
, Pr3+
mixed crystal
as a perspective upconversionally
pumped UV active medium
18.20
18.40
TuI-17 M. Lezhnina
Luminescent cationic and anionic
species in sodalites
TuII-17 O. R. Akhtyamov
Ultrashort pulse UV lasers based on
Ce3+
activated LiCaAlF6 and LiSrAlF6
crystals
18.40
19.00
TuI-18 Ch. Gadermaier
Electron Dynamics in Single- and Few-
Layer MoS2
TuII-18 L. A. Nurtdinova
Photodynamic processes and laser
performance of Ce:LiYLuF4
19.00
20.30 Poster session I
9
18 September
Advances of spectroscopy of optical centers and spin ensembles
9.30
10.00
We-1 G. Boulon Advances of polycrystalline transparent laser
ceramics
10.00
10.30
We-2 A. Meijerink Luminescence of lanthanide doped nanocrystals: new
systems, old theories and new opportunities
10.30
11.00
We-3 V. M. Agranovich
Hybrid Resonant Organic-Inorganic Nanostructures
for Novel Light Emitting Devices and Solar Cells 11.00
11.30
We-4 D. Caurant Spectroscopic investigations on glasses and ceramics
for nuclear waste immobilization
11.30
11.50 Coffee break
11.50
12.20
We-5 A. Gorokhovsky Micro-luminescence spectroscopy of Xe optical
center in diamond: production, structure and zero-
phonon line broadening
12.20
12.50
We-6 B. Barbara Quantum spin-dynamics and decoherence examined
in terms of the classical Landau-Zener model
12.50
13.10
We-7 E. I. Baibekov Decoherence in the spin ensemble driven by
microwaves
13.10
13.40
We-8 V. V. Ovsyankin The nonlinear coherent spontaneous emission upon
mixing of the 2D-exciton material waves
Lunch
15.00 Excursion
19 September
Spectroscopy of multiferroics and nanocrystals, interconfigurational bands
9.30
10.00
Th-1 A. A. Mukhin Magnetic excitations and magnetoelectric phenomena
in rare-earth borates
10.00
10.30
Th-2 A. Pimenov Magnetic and magnetoelectric excitations in
multiferroic rare earth manganites
10.30
11.00
Th-3 A A. Kornienko Definition of odd symmetry crystal field parameters
from optical spectra
11.00
11.20
Th-4 S. Klimin Series of phase transitions in IR-spectra of
multiferroic TbMnO3
11.20
11.40 Coffee break
11.40
12.10
Th-5 S. P. Feofilov
Size effects in fluorescence of Сe3+
ions in
nanocrystals
12.10
12.40
Th-6 K. K. Pukhov Luminescent characteristics of nanocomposites based
on the doped nanoparticles
12.40
13.10
Th-7 L. E. Bausá Enhancement of the nonlinear response and
spontaneous emission of Nd3+
doped LiNbO3 by
silver nanoparticles
13.10
13.30
Th-8 N. A. Kulagin Spectral Properties of ME – RE Ions in Quasi-
Ordered Nano-Structures on Oxide Surface
Lunch
15.00
15.30
Th-9 M. Grinberg Determination of energies of localized states related
to Ln3+
and Ln2+
ions with respect to bandgaps of the
host by high pressure spectroscopy
10
15.30
16.00
Th-10 M. Dramićanin Rare Earth Oxide and Orthovanadate Up-conversion
Nanoparticles: Synthesis and Emission Properties
16.00
16.20
Th-11 Yu.V. Orlovskii
Multiphonon Relaxation Accelerated by Energy
Migration in the Hydroxylated Rare-Earth Doped
Nanoparticles
16.20
16.40
Th-12 S. A. Antoshkina Structure, spectroscopic and luminescent properties
of Y(P,V)O4:Er nanophosphors
16.40
17.00 Coffee break
17.00
17.30
Th-13 B. V. Shulgin Bulk, fibercrystal and nanocomposite scintillation
materials
17.30
18.00
Th-14 K. V. Ivanovskikh VUV spectroscopic study of rare earth impurity
trapped and regular excitons in fluorides by
synchrotron radiation
18.00
18.20
Th-15 V. N. Makhov Luminescence of YAG Doped with Eu, Yb and Mn
Ions under VUV Excitation
18.20
18.40
Th-16 E. A. Radzhabov 4fn-4f
n−15d line broadening in absorption spectra of
Ce3+
, Pr3+
, Tb3+
in CdF2
19.00
20.30 Poster session 2
20 September
9.30
9.50
Fr-1 E. M.Alakshin The annealing of PrF3 nanoparticles by microwave
irradiation
9.50
10.10
Fr-2 R. M. Rakhmatullin EPR, optical and dielectric spectroscopy of Er ions
doped cerium dioxide nanoparticles
10.10
10.30
Fr-4 T. P. Gavrilova Electron spin resonance in GdMnO3/SrTiO3 thin film
10.30
10.50
Fr-5 S. K. Sharma
Localized mechanism of charge trapping around Cr3+
in ZnGa2O4:Cr3+
long-lasting phosphor for in vivo
imaging
10.50
11.10
Fr-6 M. M. Mezdrogina The sensitization of the luminescence introcenter 4f
transition of Er in crystalline ZnO-films doped with
Ce, Yb, Er
11.10
11.30 Coffee break
11.30
12.00
Fr-7 Y. Sukhorukov Magnetotransmission and magnetoreflection of
unpolirizad light in magnetic semiconductors
12.00
12.20
Fr-8 R. Y. Shendrik
Divalent cerium and praseodymium ions induced by
x-ray irradiation in fluoride crystals
12.20
12.40
Fr-9 I. I. Leonidov Ab Initio Study of Structural and Vibrational
Properties of Y2CaGe4O12 Optical Host
12.40
13.00
Fr-10 V. Lisin Modulation of an Echo Shape by a Pulsed
Perturbation as a New Spectroscopy Method
13.00 Symposium closing
Lunch
11
Poster session I PI_1 Effects of non-linear vibronic interaction on orbital and magnetic structures
of BiMnO3
L.E. Gonchar1,2)
, A.E. Nikiforov2)
1)Ural State University of Railway Transport, 620034, 66, Kolmogorov St., Ekaterinburg,
Russia 2)
Ural Federal University, 620002, 19, Mira St., Ekaterinburg, Russia
PI_2 Electronic structure and origin of luminescence in Bi-containing phosphates
and molybdates
Yu. Hizhnyi1)
, S. Nedilko1)
, V. Chornii1)
, T. Nikolaenko
1), M. Slobodyanik
1),
K. Terebilenko1)
, V. Boyko2)
, V. Sheludko3)
1) Taras Shevchenko National University of Kyiv, 64 Volodymyrska st., 01601 Kyiv,
Ukraine 2)
National University of Life and Environmental Sciences of Ukraine, 5 Geroiv
Oborony st., 03041 Kyiv, Ukraine 3)
Oleksandr Dovzhenko Hlukhiv National Pedagogical University, 24 Kyjevo-
Moscovs’ka St., 41400 Glukhiv, Ukraine
PI_3 Electronic structure and origin of luminescence of undoped and RE-doped
PbMoO4 and Pb2MoO5 crystals
V. Chornii1)
, S. Nedilko1)
, Yu. Hizhnyi1)
, M. Trubitsyn
2), I. Volnyanskaya
2)
1) Taras Shevchenko National University of Kyiv, 64 Volodymyrska st., 01601 Kyiv,
Ukraine 2)
Oles Honchar Dnipropetrovsk National University, Naukova Street 9, 49050,
Dnipropetrovsk, Ukraine
PI_4 Influence of f-f electron transitions on the local properties in vicinity of the
excited ions in trigonal alumo- and ferroborates
A.V. Malakhovskii1)
, S.L.Gnatchenko2)
, I.S.Kachur2)
, V.G.Piryatinskaya2)
,
A.L. Sukhachev1)
, A.E. Sokolov1)
, V.L.Temerov1)
, I.A. Gudim1)
1)
L.V. Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk,
Russia. 2)
B.Verkin Institute for Low Temperature Physics and Engineering, NAS of Ukraine,
61103 Kharkov, Ukraine.
PI_5 Magneto-optical activity of f-f transitions in trigonal alumo- and
ferroborates
A. L. Sukhachev, A.V. Malakhovskii, T.V. Kutsak, A.Yu. Strokova, A.E. Sokolov,
V.L. Temerov, I.A. Gudim.
L.V. Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk,
Russia.
PI_6 Spin-phonon and electron-phonon interactions in multiferroic RFe3(BO3)4
probed by terahertz spectroscopy
K.N. Boldyrev1)
, M.N. Popova1)
, T.N. Stanislavchuk2)
, A. Sirenko2)
,
L.N. Bezmaternykh3)
1)
Institute of Spectroscopy RAS, 142190, Troitsk, Moscow, Russia 2)
Department of Physics, New Jersey Institute of Technology, 07102, Newark, NJ,
USA 3)
Kirenskii Institute of Physics, Siberian Branch of RAS, 660036, Krasnoyarsk, Russia
12
PI_7 Low temperature behavior of f-f transitions in Nd0.5Gd0.5Fe3(BO3)4
multiferroic crystal
S.L. Gnatchenko1)
, I.S. Kachur1)
, V.G. Piryatinskaya1)
, A.V. Malakhovskii2)
,
A.L. Sukhachev2)
, I.A. Gudim2)
1)B.Verkin Institute for Low Temperature Physics and Engineering, NAS of Ukraine,
61103 Kharkov, Ukraine. 2)
L.V. Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk,
Russia.
PI_8 Modeling of the non-adiabatic effect in the 4f1 – 5d
1 absorption spectrum in
the LiYF4:Ce3+
crystal
R.Yu. Yunusov, O.V. Solovyev
Kazan Federal University
PI_9 Modeling of quadratic non-Condon effect in the 4f14
– 4f13
5d optical spectra
in the LiYF4:Lu3+
crystal
O.V. Solovyev, R.Yu. Yunusov
Kazan Federal University
PI_10 Testing downconversion effect in KGd2F7 doped with Tb3+
V.N. Makhov1)
, N.M. Khaidukov2)
1)
P. N. Lebedev Physical Institute, 119991, 53 Leninskii Prospekt, Moscow, Russia 2)
N. S. Kurnakov Institute of General and Inorganic Chemistry, 119991, 31 Leninskii
Prospekt, Moscow, Russia
PI_11 Coherent cooperative fluorescence resonance energy transfer
S. K. Sekatskii1)
, K. K. Pukhov2)
1)Laboratoire de Physique de la Matière Vivante, IPSB, BSP, Ecole Polytechnique
Fédérale de Lausanne, Lausanne, CH 1015, Switzerland 2)
Laser Materials and Technology Centre of General Physics Institute of Russian
Academy of Sciences, 38 Vavilova St., Block “4”, Moscow 119991, GSP-1, Russia
PI_12 Enhancement of hypersensitive transitions of rare-earth ions caused by an
Optical Near Field of nanoobjects
K.K. Pukhov1)
, S.K. Sekatskii2)
1)
Laser Materials and Technology Centre of General Physics Institute of Russian
Academy of Sciences, GSP-1 119991, 38 Vavilov St., Block “D”, Moscow, Russia 2)
Laboratoire de Physique de la Matière Vivante, IPSB, BSP, Ecole Polytechnique
Fédérale de Lausanne, CH 1015, Lausanne, Switzerland
PI_13 Host cations contributions to VUV excitation spectrum of Ce3+
ions 5d-4f
fluorescence in LiY1-xLuxF4 crystals
L. A. Nurtdinova1)
, K. Ivanovskikh2)
, V. V. Semashko1)
, M. F. Joubert2)
, S. L.
Korableva1)
1)
Kazan Federal University, 18 Kremlevskaya str., 420008 Kazan, Russia 2) Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de
Lyon, 69622 Villeurbanne cedex, France
13
PI_14 Yb2+
and Yb3+
optical centers in double-doped Ce3+
,Yb3+
:SrAlF5 single
crystals
A.N. Yunusova 1)
, V.V. Semashko 1)
, G.M. Safiullin 2)
, M.A. Marisov 1)
1)
Kazan Federal University, 420008, 18 Kremlevskaya street, Kazan, Russia 2)
Zavoisky Physical-Technical Institute, 420029, 10/7 Sibirsky tract, Kazan, Russia
PI_15 Metal Patterns in CaF2 Crystals
R.V. Gainutdinov1)
, A.S. Shcheulin2)
, A.E. Angervaks2)
, P.P. Fedorov3)
, A.I. Ryskin2)
1)
Shubnikov Institute of Crystallography, 119333, Leninskii pr. 59, Moscow, Russian
Federation 2)
National Research University of Information Technologies, Mechanics and Optics,
197101, Kronverskiy pr. 49, St. Petersburg, Russian Federation 3)
Prokhorov General Physics Institute, 119991, Vavilov str. 38, Moscow, Russian
Federation
PI_16 Rare-Earth Ion Reduction under Additive Coloring of CaF2:RE3+
Crystals
A.S. Shcheulin, A.E. Angervaks, T.S. Semenova, L.F. Koryakina, M.A. Petrova,
A.I. Ryskin
National Research University of Information Technologies, Mechanics and Optics,
197101, Kronverkskiy pr. 49, St. Petersburg, Russian Federation
PI_17 Effect of Ce ions on the spectral and decay characteristics of Li2O-B2O3-
P2O5-CaF2 glasses doped with rare-earth ion
D.T. Valiev 1), E. F. Polisadova
1), K. N. Belikov
2), N. L. Egorova
2)
1 National Research Tomsk Polytechnic University 634050, Lenin Avenue 30, Tomsk,
Russian Federation 2 Institute of Single Crystals NAS of Ukraine, 61001 Kharkov, Lenin Avenue 60,
Ukraine
PI_18 The spectral and decay characteristics of luminescence nano-and
microcrystals of ZnWO4 in the polymer matrix
V. M. Lisitsyn, E.F. Polisadova1), D.T. Valiev
1), I. A. Tupitsina
2), L.A. Andryushenko
2),
A.M. Dubovik2), A.G. Yakubovskaya
2)
1 National Research Tomsk Polytechnic University 634050, Tomsk, Lenin Avenue30,
Russia 2 Institute of Scintillation Materials NAS of Ukraine, 61001 Kharkov, Lenin Avenue
60, Ukraine
PI_19 Synthesis and luminescent properties of yttrium niobate X-ray phosphors
activated by europium
A.Yu. Mester1)
, A.N. Trofimov1)
, M.V. Zamoryanskaya1)
1)
Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Saint
Petersburg, Russia
PI_20 The influence of the magnetic field strength and excitation intensity on the
shape of microphotoluminescence spectra and paramagnetism of impurities in
crystalline ZnO films doped with Sm, Eu, Er
Yu.A. Shafir2)
, M.M. Mezdrogina1)
, A. Ja. Vinogradov1)
, I.N. Trapeznikova1)
,
O.V. Koplak3)
, A.J. Dmitriev3)
1)
Ioffe Physico-Technical Institute , Saint-Petersburg, Polytechnicheskaya, 26, Russia 2)
SPbSTU, Saint-Petersburg, Polytechnicheskaya, 29, Russia 3)
Institute of Problems of Chemical Physics, Chernogolovka, Russia
14
PI_21 The sensitization of Ln3+
luminescence in [2.2]paracyclophane-derived β-
diketonates
I.S. Pekareva1)
, L.N. Puntus1,2)
, K.A. Lyssenko2)
, F. Kajzar3)
1)
Kotel’nikov Institute of Radioengineering & Electronics, Russian Academy of
Sciences, 125009, 11-7 Mokhovaya, Moscow, Russia 2)
A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences, 119991, 28 Vavilov St, Moscow, Russia 3)
Université d’Angers, Institut des Sciences et Technologies Moléculaires d'Angers,
MOLTECH Anjou - UMR CNRS 6200, 2, Bd Lavoisier, 49045 Angers cedex, France
PI_22 Studying the energy dependence of intrinsic conversion efficiency of single
crystal scintillators under X-ray excitation
N. Kalyvas, I. Valais, S. David, Ch. Michail, G. Fountos, P. Liaparinos, I. Kandarakis
Technological Educational Institute of Athens/Department of Medical Instruments
Technology, 12210 Egaleo Athens, Greece
PI_23 Characterisations of new Nd3+
-doped scheelite-type molybdates for laser
materials
M. Guzik1)
, E. Tomaszewicz2)
, Y. Guyot3)
, P. Tomaszewski4)
, J. Legendziewicz1)
,
G. Boulon3)
1) Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, PL-50-383 Wroclaw,
Poland 2)
Department of Inorganic and Analytical Chemistry, West Pomeranian University
of Technology, Al. Piastów 42, PL- 71-065 Szczecin, Poland 3)
Institute Light Matter, UMR5306 CNRS-University of Lyon1, University of Lyon,
69622 Villeurbanne, France 4)
Institute of Low Temperature and Structure Research,PAS,Okolna 2,50-422
Wroclaw, Poland
PI_24 Phonon spectra of YTiO3 and Y2Ti2O7: ab initio calculations V.A. Chernyshev, V.P. Petrov, A.E. Nikiforov
Ural Federal University, 620002, Ekaterinburg, Russia
PI_25 Valence states of cations in nanostructured transition metal oxides studied
by means of soft X-ray absorption spectroscopy
V. V. Mesilov, V. R. Galakhov, B. A. Gizhevskii
Institute of Metal Physics, Ural Division of the Russian Academy of Sciences, 620990,
S. Kovalevskaya str. 18, Yekaterinburg, Russia
PI_26 Luminescent spectroscopy of triple-charged rare earth ions incorporated in
lead tungstate scintillator crystals
O.V. Chukova, S.G. Nedilko
Physics Faculty, Taras Shevchenko National University of Kyiv, 4-b, acad. Hlushkov
Ave., 03680, Kyiv, Ukraine
15
PI_27 Dependence of Luminescent Properties of Rare Earth Ions Incorporated in
Vanadate Matrices on Ways of Charge Compensation
S.G. Nedilko1)
, O.V. Chukova1)
, V.P. Scherbatsky1)
, V.P. Sheludko2)
,
S.V. Virko3)
1)
Physics Faculty, Taras Shevchenko National University of Kyiv, 4-b, acad. Hlushkov
Ave., 03680, Kyiv, Ukraine 2)
Olexander Dovzhenko Glukhiv State Pedagogical University, Glukhiv, Ukraine 3)
Institute of Semiconductor Physics, NAS of Ukraine, 45, Nauki Ave, 03680 Kyiv,
Ukraine
PI_28 Study of photoluminescence polarization of organic crystals
T. Prutskij1)
, M. J. Percino1)
, T. Perova2)
1)
Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Privada 17
Norte, No 3417, col. San Miguel Hueyotlipan, 72050, Puebla, Pue., México 2)
Department of Electronic and Electrical Engineering, University of Dublin, Trinity
College, Dublin 2, Ireland
PI_29 A glow of OH and OD radicals upon mechanical destruction of the
hydrated terbium and cerium sulfates in argon medium
A. A. Tukhbatullin, M. R. Muftakhutdinov, A. M. Abdrakhmanov, G. L. Sharipov
Institute of Petrochemistry and Catalysis RAS, 450075, 141, pr. Oktyabrya, Ufa,
Russia
PI_30 Energy transfer kinetic in nanocrystals doped with rare earth and
transition metal ions
Glushkov N. A.
Laser Materials and Technology Research Center at Prokhorov General Physics
Institute, RAS, 119991, Vavilov Str. 38, Moscow, Russia
PI_31 Energy transfer in dye-doped nanoparticles from Ln3+
complexes
L.Yu.Mironov, E.B.Sveshnikova, V.L.Ermolaev.
NRU ITMO, 197101, Saint-Petersburg, Russia
PI_32 Erbium doped SrTiO3 crystals: optical spectroscopy
A.P. Skvortsov1)
, N.K. Poletaev1)
, Z .Potucek2)
, L. Jastrabik2)
, A. Dejneka2)
,
V.A.Trepakov1,2)
1)
Ioffe Physical-Technical Institute RAS, 194 021, Politekhnicheskaya 26, Saint-
Petersburg, Russia 2)
Institute of Physics AS CR, Na Slovance 2, 182 21 Praha 8, Czech Republic
PI_33 Study of absorption spectra of Li6Y(BO3)3:Er3+
crystals
Á. Péter1)
, K. Polgár1)
, N. Poletaev2)
, A. Skvortsov2)
1)
Institute for Solid State Physics and Optics, Wigner Research Centre for Physics of
HAS, Konkoly-Thege M. 29-33, Budapest, Hungary 2)
Ioffe Physical-Technical Institute RAS, 194 021, Politekhnicheskaya 26, Saint-
Petersburg, Russia
PI_34 Synthesis, crystal structure and luminescence properties of
CaY2Ge3O10:Ln3+
, Ln = Eu, Tb
O.A. Tarasova, L.L. Surat, M.A. Melkozerova, A.P. Tyutyunnik, I.I. Leonidov, V.G.
Zubkov
Institute of Solid State Chemistry, UB RAS, 620990, Ekaterinburg, Russia
16
PI_35 Dependences of optical spectra of UV irradiated crystals Na4Y6F22:Ce3+
,
Na4Y6F22:Ce3+
,RE3+
(RE3+
: Yb3+
, Eu3+
) versus temperature
D.I. Tselischev, A.K. Naumov, E.Yu. Tselischeva, S.L. Korableva
Kazan Federal University,420008, Kremlevskaya 18, Kazan, Russia
PI_36 The effect of the magnetic field strength and excitation intensity on the
shape of the micro-photoluminescence spectra of the MQW structures on the
InGaN/GaN base doped with Eu, Sm and Eu+Sm
M. M. Mezdrogina1)
, M. V. Eremenko1)
, E. I. Terukov1)
, Yu.V. Kozhanova2)
,
O. V. Koplak3)
, A.J. Dmitriev3)
1)
Ioffe Physiko-Technical Institute, 194021, Saint-Petersburg, Polytechnicheskaya 26,
Russia 2)
S-PbSPU, Saint-Petersburg, 194021, Saint-Petersburg, Polytechnicheskaya 29,
Russia 3)
Institute of Problems of Chemical Physics, Chernogolovka, Russia
PI_37 Intensity of luminescence in visible and infrared spectrum range in
heterostructures n-Si/p-SiGe fabricated by direct wafer bonding with
simultaneous Er and Eu doping
M.M. Mezdrogina, R.V. Kuzmin, M. V. Eremenko, L.S. Kostina, E. I. Beliakova
Ioffe Physiko-Technical Institute, 194021, Saint-Petersburg, Polytechnicheskaya 26,
Russia
PI_38 Spectral-kinetic properties of Nd3+
ions doped series
LiY1-xLuxF4 (x=0 – 1) mixture crystals
A.K. Naumov, R.D. Aglyamov, D.I. Tselischev, E.Yu. Tselischeva, M.A. Marisov,
A.S. Nizamutdinov, V.V. Semashko, A.V. Lovchev, O.A. Morozov, V.N. Efimov,
S.L. Korableva
Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russia
PI_39 Fluctuation kinetics of luminescence hopping quenching of Ce3+
5d level in
YPO4·0.8H2O nanocrystals
A.V. Popov1,2)
, Yu.V. Orlovskii1,2)
, A.S. Vanetsev1)
, O.M. Gaitko3)
,
E.O. Orlovskaya2)
, Ilmo Sildos1)
1)Institute of Physics, University of Tartu, 51014, 142 Riia str., Tartu, Estonia
2)General Physics Institute of RAS, 119991, 38 Vavilov str., Moscow, Russia
3)Chemistry Department of Moscow State University, 119992, 3 Leninskie Gory,
Russia
PI_40 Spectroscopy of the 5d1-4f
1 transitions of Ce
3+ in yttrium phosphate
nanocrystals
A.V. Popov1,2)
, Yu.V. Orlovskii1,2)
, C.-G. Ma1,3)
, A.S. Vanetsev1)
, O.M. Gaitko4)
,
E.O. Orlovskaya2)
, S.Lange1)
, Ilmo Sildos1)
1)Institute of Physics, University of Tartu, 51014, 142 Riia str., Tartu, Estonia
2)General Physics Institute of RAS, 119991, 38 Vavilov str., Moscow, Russia
3)College of Mathematics and Physics, Chongqing University of Posts and
Telecommunications, 400065, 2 Chongwen Road, Chongqing, P.R. China 4)
Chemistry Department of Moscow State University, 119992, 3 Leninskie Gory,
Russia
17
PI_41 Optical spectroscopic study of the crystallization of B2O3:La2O3 glasses
doped with Nd3+
or Eu3+
D.S. Pytalev1)
, D. Caurant2)
1)
Institute of Spectroscopy, Russian Academy of Sciences, 142190, 5 Fizicheskaya St.,
Moscow, Troitsk, Russian Federation 2)
Laboratoire de Chimie de la Matière Condensée de Paris (UMR CNRS 7574) Ecole
Nationale Supérieure de Chimie de Paris (Chimie-ParisTech), 75005, 11 rue Pierre et
Marie Curie, Paris, France
PI_42 High-resolution optical spectroscopy of YPO4 doped with Tm3+
or Er3+
D.S. Pytalev1)
, M.N. Popova1)
, B.Z. Malkin2)
, M. Bettinelli3)
1)
Institute of Spectroscopy, Russian Academy of Sciences, 142190, 5 Fizicheskaya
St.,Moscow, Troitsk, Russian Federation 2)
Kazan (Volga Region) Federal University, 420008, 18 Kremlyovskaya St., Kazan,
Russian Federation 3)
Dipartimento di Biotecnologie, University of Verona and INSTM, 37134, Verona,
Italy
PI_43 Ceramic planar waveguide structures for amplifiers and lasers
V.A. Konyushkin, A.N. Nakladov, D.V. Konyushkin, M.E. Doroshenko,
V.V. Osiko, A.Ya. Karasik
Prokhorov General Physics Institute Russian Academy of Sciences, 119991, Vavilov
Str., 38, Moscow, Russia.
PI_44 Site-selective luminescence spectroscopy of rare earth ion doped TiO2
nanoparticles
Ž. Antić, M.G. Nikolić, M. Marinović-Cincović, M.D. Dramićanin
Institute of Nuclear Sciences Vinča, University of Belgrade, P.O.Box 522, 11001
Belgrade, Serbia
PI_45 Refractive index at the nanoscale
A . Aubret, J. Houel, A. Pillonnet, G. Ledoux, D. Amans, C. Dujardin, F. Kulzer
Institut Lumière Matière, UMR5306, Université Lyon 1-CNRS, Université de Lyon,
69622 Villeurbanne cedex, France
PI_46 Interconfigurational 5d-4f luminescence of Pr3+
in phosphate hosts
Mattia Trevisani1)
, Konstantin Ivanovskikh2)
, Fabio Piccinelli1)
, Marco Bettinelli1)
1)
Laboratory of Solid State Chemistry, Department of Biotechnology, University of
Verona, and INSTM, UdR Verona, Strada Le Grazie 15, 37134 Verona, Italy 2)
Department of Physics and Astronomy, University of Canterbury, Private Bag 4800,
Christchurch 8020, New Zealand
PI_47 Laser spectroscopy of the Mn4+
– Mn4+
ion pairs in SrTiO3 crystal
L. R.Gilyazov1)
, S. I.Nikitin1)
, R. V.Yusupov1)
, A. Dejneka2)
, V. A.Trepakov2,3)
1)
Kazan Federal University, Kremlevskaya 18, Kazan, Russia 2)
Institute of Physics AV CR, Na Slovance 2, 18221, Prague 8, Czech Republic 3)
Ioffe Physical-Technical Institute RAS, 194021 St-Petersburg, Russia
PI_48 Selective Laser Spectroscopy of BaF2:Yb3+
Crystals
S. L. Korableva, I. E. Mumdzhi, S. I. Nikitin
Kazan Federal University, 420008, Kremlevskaya 18 St, Kazan, Russia
18
PI_49 Optical properties and photoinduced magnetism in -Fe2O3 semiconductor
nanoparticles formed in liquid crystalline poly(propylene imine) dendrimer
N.E. Domracheva1)
, V.E. Vorobeva1)
, A.V. Pyataev2)
, M.S. Gruzdev3)
1)
Zavoisky Kazan Physical-Technical Institute, Russian Academy of Science, 420029,
Sibirsky Tract 10/7, Kazan, Russia 2)
Kazan Federal University, 420008, Kremlyovskaya St. 18, Kazan, Russia 3)
G.A. Krestov Institute of Solution Chemistry, Russian Academy of Science, 153045,
Akademicheskaya St. 1, Ivanovo, Russia
PI_50 Yb2+
content in laser CaF2:Yb3+
crystals and ceramics
A.S. Shcheulin1)
, A.E. Angervaks1)
, P.P. Fedorov2)
, V.M. Reiterov3)
,
E.A. Garibin3)
and A.I. Ryskin1)
1) National Research University of Information Technologies, Mechanics and Optics,
197101, Kronverkskiy pr. 49, St. Petersburg, Russian Federation 2)
General Physics Institute, Moscow, Russian Federation 3)
INCROME Ltd., ul. Babushkina 36, 192171, St. Petersburg, Russian Federation
Poster session II
PII_1 Molecular structure and magnetic properties of Mn
2+-Ag
2+ pairs formed in
BaF2 crystals: EPR data
E.R. Zhiteitsev1)
, V.A. Ulanov1,2)
, R.R. Zainullin2)
, A.M. Sinitsyn2)
1)
Zavoiskii Kazan Physical Technical Institute, Kazan, Russia 2)
Kazan State Power Engineering University, Kazan, Russia
PII_2 EPR observation of lattice instabilities in narrow gap semiconductor PbTe
doped by Mn2+
impurity ions
V.A. Ulanov1,2)
, A.M. Sinitsyn1)
, R.R. Zainullin1)
, E.R. Zhiteitsev2)
1)
Kazan State Power Engineering University, Kazan, Russia 2)
Zavoiskii Kazan Physical Technical Institute, Kazan, Russia
PII_3 Fe3+
-Cl-, Fe
3+-Br
-, Fe
3+-О
2-, Fe
3+-OH
- dimer centers in the ferroelectric lead
germanate
V. A. Vazhenin, A. P. Potapov, A. V. Fokin, and M. Yu. Artyomov
Institute of Physics and Applied Mathematics, Ural Federal University, Yekaterinburg,
Russia
PII_4 Quasi-cubic (tetragonal) Gd3+
centers in Ca1 – xYxF2+ x
V. A. Vazhenin, A. P. Potapov, A. V. Fokin, and M. Yu. Artyomov
Institute of Physics and Applied Mathematics, Ural Federal University, Yekaterinburg,
Russia
PII_5 Anisotropy of the g-tensor and spin-spin interaction in dimer
dysprosium(III) complex
R. Galeev1)
, A. Sukhanov1)
, R. Eremina1)
, V. Voronkova1)
, A. Baniodeh2)
, A. K.
Powell2)
1Zavoisky Physical-Technical Institute RAS, Kazan, Russian Federation
2Karlsruhe Institute of Technology, University of Karlsruhe, Karlsruhe, Germany
19
PII_6 EPR of [Fe2Dy2(OH)2(teaH)2(R-C6H4COO)6] clusters, R = p-NC, m-NC
A. Sukhanov1)
, V. Voronkova1)
, A. Baniodeh2)
, A. K. Powell2)
1Zavoisky Physical-Technical Institute RAS, Kazan, Russian Federation
2Karlsruhe Institute of Technology, University of Karlsruhe, Karlsruhe, Germany
PII_7 EPR investigations of 3d-4f interactions in trinuclear cluster Dy2Fe
A. Sukhanov1)
, V. Voronkova1)
, A. Baniodeh2)
, A. K. Powell2)
1)Zavoisky Physical-Technical Institute, Kazan, Russian Federation
2)Karlsruhe Institute of Technology, University of Karlsruhe, Karlsruhe, Germany
PII_8 ESR linewidth near the nematic-smectic transition
B.M. Khasanov
Kazan Federal University, Institute of Physics, Kazan, Russia
PII_9 Spin-crossover Schiff-base complexes Fe(III). The effect of laser irradiation.
I.V. Ovchinnikov1)
, T.A. Ivanova1)
, N.N.Efimov2)
, O.A. Turanova1)
, G.I. Ivanova1)
,
A.A.Sukhanov1)
, L.V. Mingalieva1)
1)
Zavoisky Physical-Technical Institute RAS, Kazan, Russia 2)
NS Kurnakov Institute of General and Inorganic Chemistry RAS, Moscow, Russia
PII_10 Submillimeter EPR spectroscopy of terbium impurity ions in synthetic
forsterite
A.A. Konovalov1)
, K.A. Subbotin2)
, V.F. Tarasov1)
, E.V. Zharikov2,3)
1)
Kazan Zavoisky Physical-Technical Institute RAS, Kazan, Russia 2)
Prokhorov General Physics Institute RAS, Moscow, Russia 3)
Mendeleev University of Chemical Technology of Russia, Moscow, Russia
PII_11 Electron-nuclear energy levels anticrossings in Al2O3:V3+
G.S.Shakurov
Kazan Physical Technical Institute, Kazan, Russia
PII_12 EPR of Gd3+
in micro- and nanoscale LaF3 particles
A.M. Sabitova, E.M. Alakshin, R.R. Gazizulin, D.G. Zverev, A.V. Klochkov, S.L.
Korableva, A.A. Rodionov, K.R. Safiullin, M.S. Tagirov
Kazan (Volga region) Federal University, Kazan, Russia
PII_13 EPR of Gd157
in CaWO4. The influence of the implicit and explicit
contributions on the parameters b20, P2
0
A.D. Gorlov1)
, I.N. Kurkin2)
1)
Ural Federal University, INS, Ekaterinburg, Russia 2)
Kazan Federal University, Institute of Physics, Kazan, Russia
PII_14 Clusters of rare-earth ions in the mixed fluoride crystals studied by EPR
L.K. Aminov, M.R. Gafurov, I.N. Kurkin, A.A.Rodionov
Institute of Physics, Kazan Federal University, Kazan, Russia
PII_15 Transient nutations in Nd-doped CaWO4 crystal
E.I. Baibekov1)
, M.R. Gafurov1)
, D.G. Zverev1)
, I.N. Kurkin1)
, B. Barbara2)
1)
Kazan Federal University, Kazan, Russian Federation 2)
Institut Néel, CNRS and Université Joseph Fourier, Grenoble, France
20
PII_16 Hyperfine structure in the infrared absorption spectra of CaWO4:Ho3+
E.P. Chukalina, M.N. Popova
Institute of Spectroscopy RAS, Troitsk, Moscow, Russian Federation
PII_17 Size-dependent crystal field distortions in yttrium doped nanocrystalline
ceria
R. M. Rakhmatullin1)
, L. K. Aminov1)
, I. N. Kurkin1)
, R. Böttcher2)
, A. Pöppl2)
, S. Sen3)
1)
MRS Laboratory, Kazan State University, Kazan, Russia 2)
Faculty of Physics and Earth Sciences, University of Leipzig, Leipzig, Germany 3)
Department of Chemical Engineering and Materials Science, University of California
at Davis, California, USA
PII_18 An X- and Q-band Fe3+
EPR Study of Nanoparticles of Magnetic
Semiconductor Zn1-xFexO
Sushil K. Misra,1)
S. I. Andronenko,2)
A. Thurber,3)
A. Punnoose,3)
A. Nalepa4)
1)
Physics Department, Concordia University, Montreal, Canada 2)
Physics Institute, Kazan Federal University, Kazan, Russian Federation 3)
Department of Physics, Boise State University, Boise, U.S.A 4)
Max Planck Institute for bioinorganic chemistry, Mülheim um der Ruhr, Germany
PII_19 High-Frequency EPR of Er3+
ions in YAG
H.R. Asatryan1)
, G.S. Shakurov2)
1)
Ioffe Physical-Technical Institute, St-Petersburg, Russia 2)
Kazan Physical Technical Institute, Kazan, Russia.
PII_20 Nano-Hydroxyapatite as studied by multi-frequency (9 and 94 GHz) EPR
and ENDOR
T.B. Biktagirov1)
, M.R. Gafurov1)
, G.V. Mamin1)
, S.B. Orlinskii1)
, A.A.Rodionov1)
,
B.V. Yavkin1)
, E.S. Klimashina2)
, V.I. Putlayev2)
1)
Institute of Physics, Kazan Federal University, Kazan, Russia 2)
Department of Chemistry, Moscow State University, Moscow, Russia
PII_21 Impact of random lattice deformations on low-temperature spectral and
magnetic properties of Tb2Ti2O7 pyrochlore
V.V. Klekovkina, B.Z. Malkin
Kazan Federal University, Kazan, Russia
PII_22 Spectral and magnetic properties of orthorhombic oxides SrR2O4 (R=Dy,
Er, Ho, Yb)
D.F. Nabiullin, B.Z. Malkin
Institute of physics, Kazan Federal University, Kazan, Russian Federation
PII_23 Studies of natural bornite by nuclear-resonance spectroscopy
R.R. Gainov1,2)
, V.V. Klekovkina1)
, A.V. Dooglav1)
, F.G. Vagizov1)
,
V.A. Golovanevskiy3)
, I.N. Pen’kov1)
, G. Klingelhöfer2)
, V. Ksenofontov2)
1)
Kazan Federal University, Kazan, Russian Federation 2)
Johannes Gutenberg University of Mainz, Mainz, Germany 3)
Curtin University, 6008, Kent Street, Bentley, Perth, Australia
21
PII_24 Optical and EPR spectroscopy of NicMg1-cO solid solutions
N. Mironova-Ulmane1)
, V. Skvortsova1)
, M.G. Brik2)
, I.Sildos2)
, T. Kärner2)
1) Institute of Solid State Physics, University of Latvia, Riga, Latvia
2) Institute of Physics, University of Tartu, Tartu, Estonia
PII_25 Magnetic resonance and optical spectroscopy of the tetragonal Yb3+
center
in KZnF3
M.L. Falin1,2)
, K.I. Gerasimov1,2)
, V.A. Latypov1)
, A.M. Leushin2)
,
S. Schweizer3)
, J.-M. Spaeth3)
1)
Kazan Zavoisky Physical-Technical Institute, Kazan, Russian Federation 2)
Kazan (Volga Region) Federal University, Kazan, Russian Federation 3)
Physics Department, University of Paderborn, Paderborn, Germany
PII_26 EPR of Dy3+
, Er3+
and Yb3+
in Cs2NaBF6 (B = Y, Sc) single crystals
M.L. Falin1,2)
, V.A. Latypov1)
, N.M. Khaidukov3)
1)
Kazan Zavoisky Physical-Technical Institute, Kazan, Russian Federation 2)
Kazan (Volga Region) Federal University, Kazan, Russian Federation 3)
Institute of General and Inorganic Chemistry, Moscow, Russian Federation
PII_27 Multifrequency EPR study of the photoinduced centers in KTaO3 crystal
D.G.Zverev1)
, R.V.Yusupov1)
, A.A.Rodionov1, P.P.Syrnikov
2), V.A.Trepakov
2,3)
1) Kazan Federal University, Kremlevskaya 18, Kazan, Russia
2) Ioffe Physical-Technical Institute RAS, 194021 St-Petersburg, Russia
3) Institute of Physics AV CR, Na Slovance 2, 18221, Praha 8, Czech Republic
PII_28 Multipole interactions between Tm3+
ions in LiTmF4
I.V. Romanova, B.Z. Malkin, M.S. Tagirov
Kazan Federal University, Kazan, 420008, Kremlevskaya 18, Russian Federation
PII_29 Trivalent ions of zirconium and hafnium in yttria ceramics
V.I. Solomonov, A.V. Spirina
Institute of Electrophysics of the Ural Branch of RAS, Ekaterinburg, Russia
PII_30 Thermodynamics of Ising rare earth magnet in the static fluctuation
approximation
A.A. Khamzin, R.R. Nigmatullin
Kazan (Volga Region) Federal University, Kazan, Russia
PII_31 Shift of the atomic spectra in the rotatory reference frame
T.A.Kudykina, A.I. Pervak.
“Ukraina” University, Kyiv, Ukraine
PII_32 Influence of conduction band energy on the level structure of transition
metal ions
N.R. Rudoman, Е.N. Tumayev
Kuban State University, Krasnodar, Russia
22
PII_33 Evaluation of absorption spectrum of trivalent chromium doped lithium
niobate crystal
К.S. Avadov, М.V. Sukachev, Е.N. Tumayev
Kuban State University, Krasnodar, Russia
PII_34 Kinetics of up-conversion of electronic excitations in active media of solid-
state lasers
I.V. Kochubey, М.V. Sukachev, Е.N. Tumayev
Kuban State University, Krasnodar, Russia
PII_35 Changes in optical properties of UV irradiated Ce-doped KY3F10 and
double-doped KY3F10:Ce3+
,Yb3+
crystals versus temperature
E.Yu. Tselischeva, A.K. Naumov, D.I. Tselischev, S.L. Korableva
Kazan Volga Federal University, Kazan, Russia
PII_36 Energy levels of Tm3+
ions in YF3 crystal
V.V. Pavlov, B.N. Kazakov, S.L. Korableva
Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russian Federation
PII_37 Photoinduced charged lattice of ruby
D. A. Bizyaev, A. A. Bukharaev, Yu. V. Vladimirtsev, K. I. Gerasimov,
N. K. Solovarov
Zavoisky Physical–Technical Institute, Kazan Scientific Center, Russian Academy of
Sciences, 420029, Sibirsky tract 10/7, Kazan, Russia
PII_38 CoO luminescence excited by synchrotron radiation
V.I. Sokolov1)
, V.A. Pustovarov2)
, V.N. Churmanov2)
, N.B. Gruzdev1)
, P.S. Sokolov3)
,
A.N. Baranov3)
1)
Institute of Metal Physics UB RAS, Ekaterinburg, Russia 2)
Ural Federal University, Ekaterinburg, Russia 3)
Lomonosov Moscow State University, Moscow, Russia
PII_39 Fluctuations of orbital order in KCuF3 related to antiphase local rotations
V. V. Iglamov, M. V. Eremin
Institut of Physics, Kazan (Volga region) Federal university, Kazan, Russian
Federation
PII_40 Multi-frequency (9 and 94 GHz) ELDOR/ ENDOR investigations
of hyperfine interactions
V. O. Erofeev, M.R. Gafurov, G.V. Mamin, S.B. Orlinskii
Institute of Physics, Kazan Federal University, Kazan, Russia
PII_41 Centres of luminescence in LiF-U crystals
M.M. Kidibaev, G.S. Denisov
Kyrgyz Academy of Sciences, Institute of Physical-Technical Problems and Material
Engineering
PII_42 Polaron in biatomic linear chain: perturbation theory approach
A.L. Larionov
Kazan Federal University, Kazan, Russian Federation
23
PII_43 EPR studies of the mechanochemically doped fluorites
I A Irisova, A A Rodionov, D A Tayurskii, and R V Yusupov
Kazan Federal University, Kazan, Russia
PII_44 Ab-initio investigation of phonon spectra of GdLiF4 compound under
hydrostatic pressure
A. V. Petrova1)
, B. Minisini2)
, O. V. Nedopekin1)
, D. A. Tayurskii1)
1)
Institute of Physics, Kazan Federal University, Kazan, Russia 2)
Institut Supérieur des Matériaux et Mécaniques Avancés du Mans, Le Mans, France
PII_45 About Coulomb interaction in systems with the delocalized electrons
O.A. Anikeenok
Kazan Federal University, Kazan, Russia
PII_46 Paramagnon-like excitations theory for magnetic properties of layered
copper oxide superconductors as obtained by resonant inelastic X-ray scattering
I.A. Larionov
Kazan Federal University, 420008, Kremlevskaya, 18, Kazan, Russia
National University of Science & Technology "MISIS", 119049, Moscow, Russia
PII_47 NQR, NMR and high field ESR investigation of the magnetic order in
InCu2/3V1/3O3
E. Vavilova1)
, M. Yakovleva1)
, M. Yehia2)
, V. Kataev2)
, T. Taetz3)
,
A. Moeller4)
and B. Buechner2)
1) Zavoisky Physical Technical Institute, RAS, Kazan, Russia
2) IFW Dresden, Dresden, Germany
3) Institut fur Anorganische Chemie, Universitaat zu Koln, Germany
4) University of Houston, Department of Chemistry and Texas Center for
Superconductivity
PII_48 EPR and ENDOR study of charge-compensated Fe3+
centers in ZnO
Yu.S. Kutin, G.V. Mamin, S.B. Orlinskii
Kazan Federal University, 420008, Kremlyovskaya St.18, Kazan, Russia.
PII_49 Submillimeter EPR spectroscopy of the Cr2+
ions in KZnF3 crystal
S.I. Nikitin1, G.S. Shakurov
2, T.R. Sharafiev
1, V.F. Tarasov
2,
R.V. Yusupov1, D.G. Zverev
1
1) Kazan Federal University, Kremlevskaya 18, 420008 Kazan, Russia
2) Zavoisky Physical-Technical Institute RAS, Sibirsky Trakt 10/7, 420029 Kazan,
Russia
24
Mo-1 Signals and noise in polarization magneto-optics
Valerii S. Zapasskii
Saint-Petersburg State University, Physics Department, Spin Optics Laboratory,
Saint-Petersburg, 198504 Russia
A paramagnet in an external magnetic field (real or effective) acquires optical anisotropy due
to orientation ordering of the spin ensemble. Axial symmetry of the perturbation and axial
(rather than polar) nature of the magnetization and magnetic field vectors dictates symmetry
of the most specific magneto-optical effects observed in the longitudinal geometry (along the
direction of magnetization) – polarization plane rotation (Faraday effect) and magnetic
circular dichroism. These effects are currently widely used for measuring magnetic properties
of the impurity ions in solids, for studying dynamics of spin-systems perturbed by external
fields, for optical detection of spin precession and other effects of collective response. All
these effects measured on real spin-systems are, however, the result of averaging over a great
number of fluctuating spins and, therefore, should fluctuate themselves. These fluctuations,
for macroscopic samples, are evidently very small, but, being detected, can provide important
information about the system in a more or less nonperturbative way.
It is noteworthy that the ratio of a regular signal to noise in contemporary magneto-
optics rapidly changes. First of all, relative magnitude of spin fluctuations increases with
decreasing size of the spin ensemble, and the noise eventually becomes comparable with its
regular response. At the same time, the highest sensitivity needed to detect magneto-optical
effects in spin micro-systems often implies increasing light intensity (to reduce relative
magnitude of the shot noise), which inevitably makes the measurements more perturbative.
In this talk, we will consider the interplay between regular response of spin systems,
their spontaneous noise, and shot noise of the photon flux, revealed in the most spectacular
form in the rapidly developing field of research – spectroscopy of spin noise.
25
Mo-2 Parametric Doppler effect in nonlinear-optical crystals and dielectrics
N. N. Rosanov1-3)
1)Vavilov State Optical Institute, 199034, Birzhevaya Liniya 12, Saint-Petersburg, Russia
2)National Research University of Information Technologies, Mechanics, and Optics, 197101,
Kronverksky prospect 49, Saint-Petersburg, Russia 3)
Ioffe Physical Technical Institute, 194021, Polytekhnicheskaya ul. 26, Saint-Petersburg,
Russia
The lowest order nonlinear optical polarization of centrosymmetric crystals and dielectrics
has the form (3)
1 2 3 E E E where (3)
is the cubic susceptibility tensor and E1-3 are electric fields
of three waves. Let E1 and E2 correspond to strong pump waves, possibly coinciding, and E3
is the field of weak probe wave with the orthogonal polarization, (E3, E1,2) = 0. Then the
pump waves induce in the medium an inhomogeneity of refractive index moving with light
velocity. This inhomogeneity acts, with respect to the probe field, as a relativistic mirror that
can produce a giant Doppler transformation of probe radiation frequency [1]. In the case of
non-coinciding frequencies of pump waves, 1 2 , the inhomogeneity is presented by two
gratings, and typically one of the gratings is superluminal and the other is subluminal [2, 3].
In the report, an analysis is presented of probe wave reflection on moving inhomogeneities of
different types. It is shown that superluminal gratings produce phase conjugation of reflected
probe wave. In a medium with IR- and UV-absorption bands the frequency of reflected
radiation can be transformed, e.g., from the main transparency band to the lower- or higher-
frequency bands. Discussed are possible applications of this parametric Doppler effect to laser
frequency transformation and to spectroscopy of pure and doped crystals and dielectrics.
[1] N. N. Rosanov, JETP Lett. 88(8), 501-504 (2008).
[2] N. N. Rosanov, JETP Lett. 95(12), 609-612 (2012).
[3] N. N. Rosanov, JETP 115(6), 962-968 (2012).
26
Mo-3 Beyond diffraction limit using upconversion
F. Pellé1)
, L. Caillat1,2)
, B. Hajj2)
, V. Shynkar2)
, J. Zyss2)
1)
LCMCP UMR 7574 CNRS/ UPMC/ Chimie Paristech, Paris, France 2)
LPQM UMR 8537 CNRS, Institut d’Alembert, ENS Cachan, Cachan, France
During the past two decades, multiphoton microscopy, mainly two-photon excitation
microscopy, has become a powerful tool for imaging biological structures, the infrared
excitation lying in the range of the therapeutic window, multiphoton microscopy allows
imaging living tissues at a higher depth than its counterpart, the Laser Scanning Confocal
Microscopy. Nonlinear processes are implemented such as multiphoton absorption mainly
two-photon absorption (TPA), multiharmonic generation mainly second harmonic generation
SHG and coherent anti-Stokes Raman scattering. All these phenomena occur under high peak
power excitation provided by femtosecond lasers. Using infrared excitation, the photostability
of commonly used optical probes (organic molecules, proteins…) is enhanced but the high
excitation power densities are photoxic providing destruction of the living tissues by
hyperthermia. On other hand, there is a need to improve the resolution of the imaging system.
This can be achieved by breaking the Abbe's diffraction law as proposed by S. Hell [1] with
the STED microscopy. If the axial and lateral resolutions are well beyond that is given by the
diffraction barrier, the experimental set up is greatly expensive and the photobleaching of the
probes is still a drawback, furthermore no multiplexing of the signal is possible for the
moment.
Presented here experimental results state that individual RE doped fluoride nanocrystals are
featuring several advantages over conventional probes used in bio and medical imaging. The
near-IR excitation wavelengths lead to a low background which improves the signal-to-noise
ratio. The absence of photo-blinking and photobleaching opens the way for their use in
tracking applications. We demonstrated that up-conversion can enhance lateral resolution by a
factor compatible with the square root of the number of photons involved in the up-
conversion excitation process. We also showed that two-, three-, and four-photon processes
can be detected down to the single particle scale [2]. From particular properties of up-
conversion, it is expected that a CW laser diode will be enough to excite the multiphoton
luminescence. Such features, in combination with existing functionalization methods, open
the way to low cost multiphoton microscope systems, using low power CW laser.
Acknowledgement
This work is supported by the EADS Foundation Project #078-A008-0909.
[1] T. A. Klar, E. Engel, S. W. Hell, Phys. Rev. E, 64 (2001) 066613.
[2] L. Caillat, B. Hajj, V. Shynkar, L. Michely, D. Chauvat , J. Zyss, F. Pellé, Appl. Phys.
Lett. 102 (2013) 143114.
27
Mo-4 Symmetry adapted approach to the dynamic Jahn-Teller problem:
advances and challenges
Boris Tsukerblat1)
, Andrew Palii 2)
, J.M. Clemente-Juan
3),
Alejandro Gaita-Ariño3)
, Eugenio Coronado3)
1)
Chemistry Department, Ben-Gurion University of the Negev, 84105 PO Box 653, Israel 2)
Institute of Applied Physics, Academy of Sciences of Moldova, 277028 Academy str, 5,
Kishinev, Moldova 3)
Instituto de Ciencia Molecular, Universidad de Valencia, 46980 Polígono de la Coma, s/n,
Spain
In context of the present-day trends studies of the nanosized systems which are at the
border between classical and quantum scales here we present a symmetry-adapted approach
aimed to the accurate solution of the dynamic Jahn-Teller (JT) problem in large scale
multimode systems, like impurity centers and clusters in crystals, molecular and biological
objects, etc. In these cases we face a very high dimension of the Hilbert space aggravated by a
poor convergence of the computational procedure with the truncated vibronic basis. The
system under consideration is supposed to consist of the set of the electronic levels of definite
symmetries ( n 21, ) mixed by the active JT and pseudo JT vibrational modes f 21 , .
The algorithm for the solution of JT problem proposed here takes full advantage from the
point symmetry arguments. The symmetry properties of the bosonic operators are taken into
account in the procedure of the construction of the so called multivibronic operators based on
the subsequent multiple Clebsch-Gordan coupling [1]. The design of the vibrational basis can
be made in general and the Gram-Schmidt orthogonalization is required at each step of the
procedure. Finally, the generated vibrational bases are coupled to the electronic ones to get
the symmetry adapted basis in which the full matrix of the JT Hamiltonian is blocked to
maximum extent.
The general approach is applied to the evaluation of the energy spectrum (hybrid
electron-vibrational states) and intervalence optical absorption in mixed valence systems
containing arbitrary number of the localized spins and itinerant electrons with the due account
for the relevant interactions including double exchange. In particular we discuss the
intriguing magnetic properties of the 2e-reduced MV dodecanuclear Keggin anion in which
the electronic pair is delocalized over twelve sites (Td) giving rise to the (1T2+
1E+
1A1)(e+t2)
(3T1+
3T2)(e+t2) combined JT/pseudo JT problems for the spin-singlet and spin-triplet states.
The financial support of the Israel Science Foundation is gratefully acknowledged (ISF, grant
no. 168/09).
[1] B. Tsukerblat, A. Palii,
J. M. Clemente-Juan, A. Gaita-Ariño, E. Coronado, Int. J.
Quantum Chem. 112 (2012) 2849.
28
Mo-5 Optical Jahn-Teller effect in impurity centers of crystals:
contribution of phonons
V. Hizhnyakov
Institute of Physics, University of Tartu, 51014, Riia 142, Tartu, Estonia
An essential feature of JTE in solids is the participation of the phonon continuum. However
existing methods are applicable only to the systems with few (usually not more than 10)
contributing vibration coordinates. In Ref. [1] O’Brien proposed an approach allowing one to
consider the multimode effects by means of a single JT-active mode (or a few of them) and an
additional quadratic coupling of vibrations H’. She presented a set of equations for the
parameters of the coupling H’. However, it remains unclear how these equations could be
solved. The concept analogous to O’Brien’s idea of the effective modes has also been used in
molecular physics, see e.g. [2]. However, in Ref. [2] the main attention was paid to the effects
caused only by these modes. The quadratic interaction H’ replacing the JT coupling with non-
totally symmetric phonons was not considered and the effects caused by phonons have not
been studied.
Here we present a method [3,4] which allows one to find the quadratic interaction H’
explicitly supposing that it is weak as compared to the main vibronic coupling. We apply the
method for calculation of optical spectra of impurity centers in crystals with the JTE and
pseud-JTE in the excited state. The method is fully quantum-mechanical,- the main
interaction is considered using the quantum-mechanical basis of the vibronic states of the
Jahn-Teller-active local mode(s), the effect of coupling H’ is considered by means of the
cumulant expansion of the evolution operator. It is shown that, as a result of the interaction
H’, every vibronic line in the preliminary spectrum is replaced by the phonon-assisted band.
The intensities, positions and the shapes of the bands are found.
To illustrate the results, multiple computed spectra are presented. Calculated examples
include absorption and resonant Raman scattering excitation spectra. A number of specific
quantum effects, such as the nonadiabaticity-induced enhancement of the Raman scattering at
high-energy excitation, the size effect of the final state, the interference of different channels
of scattering, the Fermi resonances in the conical intersection, and others, were shown to
become apparent in the calculated spectra. The vibronic interaction with phonons essentially
determines the structure of the spectra. We also apply the method for calculating of the
relaxation of a Jahn-Teller system (including the passing it through the conical intersection)
due to emission of phonons to the bulk.
The research was supported by the project IUT2-27 and by the European Union
through the European Regional Development Fund (project 3.2.0101.11-0029).
[1] M. O’Brien, J. Phys. C: Solid State Phys. 5 (1972) 205.
[2] E. Gindensperger, I. Burghardt, L. S. Cederbaum, J. Chem Phys. 124 (2006) 144104.
[3] V. Hizhnyakov, K. Pae, T. Vaikjärv. Chem. Phys. Lett. 525-526 (2012) 64
[4] K. Pae and V. Hizhnyakov, J. Chem. Phys. 138 (2013) 104103
29
Mo-6 Spectral signatures of random deformations in crystals
M.N. Popova
Institute of Spectroscopy Russian Academy of Sciences, 142190, 5 Fizicheskaya St., Troitsk,
Moscow, Russian Federation
Zero-phonon optical intra-configuration 4f-4f transitions of rare-earth (RE) ions in real
crystals are always inhomogeneously broadened. In many cases this broadening is very small
which offers a possibility to study fine spectral line structures of different origin, using high-
resolution optical spectroscopy. This talk presents results of recent joint studies of random
lattice deformations in a series of rare-earth-doped crystals, performed by the high-resolution
spectroscopy group in the Institute of Spectroscopy, several crystal-growth groups from
different institutions, and theoreticians from the Kazan (Volga Region) Federal University.
Random lattice deformations shift the frequency of a singlet-singlet optical transition and, as
the deformation tensor components with opposite signs are equally probable, an
inhomogeneously broadened spectral line of such transition has a symmetric shape. It is
different with an optical transition involving at least one degenerate electronic energy level.
As in the case of the Jahn-Teller effect, there always exist deformations that lift the
degeneracy. Provided that the coupling of the degenerate electronic level with the low-
symmetry deformations dominates over its coupling with totally symmetric deformations
(which cause level shifts), a specific deep dip appears at the center of the inhomogeneously
broadened line.
Examples will be given of experimentally
observed specific line shapes in optical spectra of
RE impurity centers of different symmetries.
LiYF4:Tm3+
single crystals with the sheelite
structure [1], zircons YPO4:Tm3+
, aluminates
LaAlO3 doped with Ho3+
or Pr3+
, as well as cubic
hexafluoroelpasolites Cs2NaYF6 and Cs2NaScF6
doped with the Kramers Yb3+
, Er3+
, or Sm3+
ions
and the non-Kramers Tm3+
ion were studied. The
resolved fine structure was detected for several
optical transitions involving a degenerate
electronic energy level (see Fig. 1). A theoretical
analysis of the measured fine structure has
provided information about random perturbations
of the crystal lattice. For all studied crystals the experimental data were well reproduced by
the calculated spectral profiles provided the width of the strain distribution function was
between 10-5
and 10-4
. The greater values of correlated with greater concentration of
impurity ions or/and greater difference in atomic radii between the host and impurity ions.
This work was supported in part by the RFBR (Grant No. 13-02-01091) and by the RAS.
[1] S. A. Klimin, D. S. Pytalev, M. N. Popova, B. Z. Malkin, M. V. Vanyunin, and S. L.
Korableva, Phys. Rev. B 81 (2010) 045113.[2] B. Z. Malkin, D. S. Pytalev, M. N. Popova, E.
I. Baibekov, M. L. Falin, K. I. Gerasimov, N. M. Khaidukov., Phys. Rev. B 86 (2012)
134110.
Figure 1 Measured and simulated (red curve)
line shapes for the transition 5(3H6, 31 cm-1)
2 (3H5, 8240 cm-1) in YPO4:Tm3+.
30
Mo-7 Vibronic interaction in ZnSe:Cr in magnetic field
N. S. Averkiev1)
, K. A. Baryshnikov1)
, I. B. Bersuker2)
, V. V. Gudkov3,4)
,
I. V. Zhevstovskikh3,5)
, V. Yu. Mayakin3)
, A. M. Monakhov1)
and M. N. Sarychev3)
1)
A.F. Ioffe Physical Technical Institute, RAS, 194021, St.-Petersburg, Russia
2) Institute for Theoretical Chemistry, The University of Texas at Austin, TX 78712, Austin,
USA 3)
Physical Technological Institute, Ural Federal University, 620002, Yekaterinburg, Russia
4) Russian State Vocational Pedagogical University, Yekaterinburg, 620012, Russia
5) Institute for Metal Physics, Ural Department of the RAS, 620990, Yekaterinburg, Russia
Ultrasonic investigation proved to be a useful method for study the Jahn-Teller (JT) effect in
crystals doped with 3d ions (see, e.g., [1]). The JT center consists of an ion with orbitally
degenerate electronic states in the field of the nearest neighbors. Most information obtained in
ultrasonic experiments is derived from the temperature dependences of attenuation )(T and
phase velocity )(Tv . Recently [2] the influence of magnetic fields on and v in ZnSe:Cr2+
in the form of resonant anomalies at 23 MHz in magnetic field kOe 2H was revealed. The
ZnSe crystal has a sphalerite structure, where Cr2+
replaces Zn, and the CrZn4Se center is
subject to the )( 2 eT JT problem with e-type global minima of the adiabatic potential
energy suface [1]. Here we report new results obtained at higher frequency ( MHz522/ )
using a specimen with higher concentration of Cr2+
(4.5×1019
cm-3
). We have observed
significant anomalies in the variation of )(H (Fig.1) and )(Hv only for the slow shear mode
propagating along the [110] axis. This mode produces tetragonal distortions of the tetrahedral
JT center. Therefore, we can state that the anomalies are caused by the interaction of
ultrasound with the JT e-type
vibronic mode. At 0H and
K 4T the dominant
mechanism of relaxation is
quantum tunneling through the
potential barriers via
orthorhombic distortions [1]. At
0H , the wave functions of the
states in different tetragonal
minima become mixed
facilitating direct transitions
between them, thus increasing the
relaxation rate 1 , decreasing
the phase velocity, and increasing
the attenuation. Comparison of
)(H (or )(Hv ) with their
magnitudes at 0H yields the magnetic field contribution to the relaxation time . This
circumstance opens new opportunities for description of the CrZn4Se properties. The work
was supported by the Russian Foundation for Basic Research (grant # 12-02-00467-a).
[1] V.V. Gudkov and I.B.Bersuker, in M.Atanasov, C.Daul, Ph.L.W.Tregenna-Piggot (eds),
Vibronic Interactions and the Jahn-Teller Effect, Springer, Heidelberg, p.143–161 (2012).
[2] V.V. Gudkov, I.B.Bersuker, S.Yasin et al. Solid State Phenomena 190, 707–710 (2012).
0 10 20 30 40 50 60
H, kOe
1.9 K
0 10 20 30 40 50 60
3 K
0 10 20 30 40 50 60
40
45
50
55
T, K
Atte
nuat
ion,
dB
/cm 4.2 K
Fig. 1. Attenuation of slow shear mode versus magnetic field at fixed
temperatures.
31
Mo-8 Rephasing-based solid state quantum memory
B. S. Ham
School of Information and Communications, Gwangju Institute of Science and Technology
(GIST), Gwangju 500-712, S. Korea
A quantum coherence control is applied to photon echoes to extend storage time and to
eliminate population inversion-caused quantum noises. Photon echoes have intrinsic storage
properties are multimode in time domain and multidimensional in space domain. The writing
time or storage bandwidth is determined by inhomogeneous broadening of the medium, where
it is normally far beyond GHz in doped solids. Due to the rephasing mechanism of the
inhomogeneously broadened atoms, the storage mechanism is in the reversibility of atoms’
dephasing. This rephasing property, however, causes a population inversion to the echoes
resulting in quantum noises such as spontaneous and stimulated emissions. Another intrinsic
drawback of photon echoes for quantum memories is a short storage time limited by atom’s
phase decay time, normally far less than a millisecond. In this talk I present a technique
eliminating the pi-pulse-caused quantum noises via double rephasing. I also present an optical
locking method to extend the storage time by applying quantum coherence control, where
optical coherence is swapped by spin coherence. Moreover, by adapting the three-pulse
photon echo property of population grating as a storage mechanism, the final storage time is
extended to spin population decay time, which is far beyond a second. Thus, this work can be
applied to quantum repeaters for long-distance quantum communications. Preliminary
experimental demonstrations are shown as a proof of principle of the ultralong quantum
memory protocol.
32
Mo-9 Logic gates and storage elements based on ion ensembles in a Pr3+
:LaF3 crystal
R. A. Akhmedzhanov, A. A. Bondartsev, L. A. Gushchin, A. G. Litvak, D. A. Sobgayda
and I. V. Zelensky
Institute of Applied Physics Russian Academy of Sciences, 603950, 46 Ul’yanov Street,
Nizhny Novgorod, Russia
The interest in quantum communication technologies is rapidly growing, therefore
there is an ongoing search for quantum systems that could serve as logic gates and memory
elements. One of the approaches is to use ensembles of rare-earth ions doped into inorganic
crystals [1,2]. These ensembles are spectrally selected within the inhomogeneously broadened
optical transition. The ensemble approach is a generalisation of the single ion approach,
similar to the ensemble quantum computer based on nuclear magnetic resonance in molecules
[3], where each molecule is a separate quantum processor and the experimentally measured
value is equal to the average over the molecule ensemble. Ion groups with differing optical
transition frequencies within the inhomogeneously broadened line correspond to different
qubits. Unlike the case of qubits based on trapped ions or atoms, where qubits are separated
spatially, rare-earth ion ensembles are separated spectrally and can be addressed in the
frequency domain, which is much simpler to implement. In addition, inorganic crystals doped
with rare-earth ions are promising candidates to use for creating quantum memories. The best
quantum memory schemes are also based on the ensemble approach. They include non-
classical photon echo schemes (atomic frequency combs, controlled reversible
inhomogeneous broadening) and schemes based on electromagnetically induced transparency.
It is important to note that using the same crystal both for quantum processors and for
quantum memories is very appealing because it would eliminate the need to transform the
frequency of photons carrying information from the processor to the storage element.
In this work we present an experimental implementation of the spectral selection
procedure in a Pr3+
:LaF3 crystal. We show that we can control the hyperfine state population
of the selected ion group. We demonstrate that the frequency corresponding to the absorption
line of the chosen spectrally selected ion group can be controllably shifted by exciting another
ion group. These results show that this system can be used to physically implement qubits and
main qubit operations.
Furthermore, we research electromagnetically induced transparency in the Pr3+
:LaF3
crystal. It is shown that by using specially prepared ion ensembles with inhomogeneous
linewidth less than the hyperfine level splitting we can obtain much higher levels of
transparency than in unprepared crystal.
Lastly, we provide an experimental implementation of optical quantum memory that is
based on using atomic frequency comb structures in the Pr3+
:LaF3 crystal. We present a way
of controlling the comb structure period (and, consequently, the echo signal reemission time)
by changing the external electric field.
[1] S. Bertaina, S. Gambarelli, A. Tkachuk, I. N. Kurkin, B. Malkin, A. Stepanov, B. Barbara,
Rare-earth solid-state qubits. Nature Nanotechnology (2007) V.2. P.39-42.
[2] A. I. Lvovsky, B. C. Sanders, W. Tittel, Optical quantum memory. Nature photonics.
(2009) V. 3. P. 706-714.
[3] G. Cory, A. F. Fahmy, T. F. Havel, Ensemble quantum computing by NMR spectroscopy.
Proceedings National Academy of Sciences USA, Computer Sciences. (1997) V. 94. P. 1634-
1639.
33
Mo-10 Spin Dynamics in Rare Earth Doped Crystals
Ph. Goldner, A. Ferrier
Condensed Matter Chemistry Laboratory, Chimie-Paristech, CNRS, Paris 6 University, 11 rue
Pierre et Marie Curie, 75005 Paris, France
Rare earth doped crystals have been recently considered as promising materials for
solid state quantum information processing. This is due to the long coherence lifetime (T2) of
their optical transitions, which can reach several ms at liquid helium temperatures [1].
Hyperfine transitions of rare earth ions can even show longer T2, up to about 10 ms [2]. When
decoupling techniques are used, coherence lifetimes can be increased by several orders of
magnitude [3,4]. These techniques include applying specific external magnetic fields in order
to obtain transitions with very small shifts with respect to magnetic field fluctuations (Zero
First Order Zeeman shift). Another efficient way to increase coherence lifetimes is to apply
sequences of RF pulses resonant with the hyperfine transition of interest in order to
compensate for slow environment fluctuations (dynamical decoupling). In view of these
favourable properties, qubits in rare earth doped materials are usually defined as a ground
state hyperfine transition. A quantum light matter interface with processing capabilities can
then be obtained by taking advantage of both optical and spin transitions and transferring
coherences between them. This leads to several applications like quantum memories for light
[5,6] or optically addressed quantum computers [7-9].
In this talk, we will present recent results obtained in our group on europium and
praseodymium doped crystals. In particular, we have observed in Pr3+
:La2(WO4)3 an increase
of the coherence lifetime of a ground state hyperfine transition coherence lifetime by nearly
three orders of magnitude by applying a suitable magnetic field [10]. We will also discuss
these decoupling techniques in the context of quantum processing applications, where one
has, for example, to fully preserve quantum states [11].
[1] R. M. Macfarlane, J. Lumin. 100, 1 (2002).
[2] A. L. Alexander, J. J. Longdell, and M. J. Sellars, J. Opt. Soc. Am. B 24, 2479
(2007).
[3] E. Fraval, M. J. Sellars, and J. J. Longdell, Phys. Rev. Lett. 95, 030506 (2005).
[4] E. Fraval, M. J. Sellars, and J. J. Longdell, Phys. Rev. Lett. 92, 077601 (2004).
[5] W. Tittel, T. Chanelière, R. L. Cone, S. Kröll, S. A. Moiseev, and M. J. Sellars, Laser
& Photon. Rev. 4, 244 (2009).
[6] I. Usmani, C. Clausen, F. Bussières, N. Sangouard, M. Afzelius, and N. Gisin, Nat.
Photonics 6, 234 (2012).
[7] J. Wesenberg, K. Mølmer, L. Rippe, and S. Kröll, Phys. Rev. A 75, 012304 (2007).
[8] J. J. Longdell, M. J. Sellars, and N. B. Manson, Phys. Rev. Lett. 93, 130503 (2004).
[9] L. Rippe, B. Julsgaard, A. Walther, Y. Ying, and S. Kröll, Phys. Rev. A 77, 022307
(2008).
[10] M. Lovrić, P. Glasenapp, D. Suter, B. Tumino, A. Ferrier, P. Goldner, M. Sabooni, L.
Rippe, and S. Kröll, Phys. Rev. B 84, 104417 (2011).
[11] X. Peng, D. Suter, and D. A. Lidar, J. Phys. B: at. Mol. Opt. Phys. 44, 154003 (2011).
34
Mo-11 Frequency-multiplexed quantum memories with read-out
on demand for quantum repeaters
N. Sinclair1)
, E. Saglamyurek1)
, H. Mallazadeh1)
, J. A. Slater
1), M. Hedges
1), M. George
2),
R. Ricken2)
, D. Oblak1)
, W. Sohler2)
, and W. Tittel1)
1) Institute for Quantum Science and Technology, and Department of Physics & Astronomy,
University of Calgary
2) Department of Physics - Applied Physics, University of Paderborn, Germany
Quantum repeaters require quantum memories that satisfy a certain number of criteria [1, 2].
These include: (i) storage and recall of members of entangled photons with high efficiency
and (ii) high fidelity, (iii) sufficiently long storage times, (iv) the capability to store multiple
photonic qubits simultaneously, and (v) the possibility to retrieve any desired qubit on
demand. Properties (iv) and (v) are generally associated with the ability to trigger the re-
emission of any previously stored qubit at a desired time [3]. In this talk we will argue that
this view is too restricted, and that it is possible to build a quantum repeater using quantum
memories that allow storage of frequency multiplexed qubits supplemented with frequency-
selective read-out on demand. Furthermore, we will report measurements based on an atomic-
frequency comb quantum memory implemented in a Ti:Tm:LiNbO3 waveguide cooled to 3K
[4, 5] that demonstrates the required on-demand readout with average fidelity of 0.95 ± 0.03,
thereby significantly violating the maximum fidelity of 0.67 possible using a classical
memory. Our demonstration constitutes an important step towards the development of a
quantum repeater.
[1] N. Sangouard, C. Simon, H. de Riedmatten and N. Gisin, Rev. Modern Phys. 83, 33
(2011).
[2] A.L. Lvovsky, W. Tittel, and B.C. Sanders, Nature Photonics 3, 706 (2009).
[3] Simon, et al. Phys. Rev. Lett. 98, 190503 (2007).
[4] M. Afzelius, C. Simon, H. de Riedmatten and N. Gisin, Phys. Rev. A 79, 052329 (2009).
[5] E. Saglamyurek et al. Nature 469, 512 (2011).
35
Mo-12 Photon echo quantum memory with Raman atomic transitions
S. A. Moiseev
Kazan Physical-Technical Institute of the Russian Academy of Sciences, 420029, Sibirsky
trakt 10/7, Kazan, Russia
Quantum memory (QM) is considered as one of the key tools in practical implementation
of some basic quantum information technologies. In particular a realization of QM in optical
region is highly important for expansion of optical quantum communications over the long
spatial distances due to using optical quantum repeater device based on the multi-qubit QMs.
A large experimental progress in optical QMs has been achieved for the ensemble based QMs
(see [1]). However a sufficiently effective robust optical QM is still a topical problem of
quantum optics. There are a few main proposals, where the photon echo approach [2,3] seems
to be quite prospective for effective quantum storage of multi-mode light fields [4,5]. In this
report, we discuss new promising properties of the photon echo QM based on the off resonant
Raman atomic transition.
At first we demonstrate an effective storage of multi-mode signal light fields characterized
by a number of pulses with different wavelengths. Here, we also analyze some possible
manipulations and control of the stored signal light fields. Then, we present a new scheme of
photon echo QM based on the off resonant atomic transition in the optical QED cavity. The
scheme possesses a number of critical advantages inherent to the off resonant Raman
interaction in optical QED cavity for deterministic control of atomic dynamics. It is shown
that such a scheme could provide a highly efficient retrieval of the signal light fields for
natural inhomogeneous broadening of atomic transition. High quantum efficiency and fidelity
is achieved within some spectral domain of the signal light fields if some optimal parameters
of the quantum memory scheme are hold while the perfect light retrieval is realized even the
time reversal light-atom dynamics is not implemented. Finally we discuss the potential
advantages of the photon echo QMs with other approaches and obtained experimental results.
[1] See quantum memory special issue in J. Phys. B: At. Mol. & Opt. Phys. 45, V.12, (2012),
ed: J.-L. Le Gouet and Sergey Moiseev. http://iopscience.iop.org/jphysb/45/12.
[2] S. A. Moiseev, and S. Kroll, Phys. Rev. Lett. 87, 173601 (2001).
[3] W. Tittel, et al., Laser & Phot. Rev. 4, 244 (2010).
[4] M. Hosseini, et al., Nature Commun. 2, 174 (2011).
[5] M. Bonarota, J.-L. Le Gouet, and T. Chaneliere, New J. Phys, 13, 013013 (2011).
36
Mo-13 Stimulated photon echo and time-reversal of optically carried signals
A. Louchet-Chauvet, H. Linget, J.-L. Le Gouët
Laboratoire Aimé Cotton, CNRS-UPR3321, bâtiment 505, 91400 Orsay, France
Stimulated photon echo (SPE) consists in sending three optical pulses into an atomic
ensemble with an inhomogeneously broadened absorption profile. The first two pulses
prepare a spectral grating within the absorption profile. The third pulse probes the grating and
is followed by an echo pulse, originating from the rephasing of the atomic coherences.
Spectral diffusion (SD) and instantaneous spectral diffusion (ISD) strongly affect the echo
intensity. SD results from the fluctuations of each atom transition frequency caused by its
interaction with the environment [1]. ISD refers to random frequency shifts of each atom
caused by laser-excitation-induced changes in the atoms environment occurring during the
SPE sequence [2]. Fundamental understanding of such mechanisms can be obtained by a
thorough investigation of the SPE dynamics.
In rare-earth ion-doped crystals, SPE is used not only for fundamental spectroscopy, but also
for RF signal processing: true-time delay [3], broadband arbitrary waveform generation [4]
and spectral analysis of RF signals [5] have been achieved with protocols derived from SPE.
We use SPE in Er3+
:YSO to perform time-reversal of optically carried signals [6]. The first
two pulses, linearly chirped with opposite chirp rates, prepare a spectral grating with a
linearly variable spectral period in the absorption profile. The input signal is transposed on a
third chirped pulse, playing the part of the third pulse in the SPE sequence. The echo pulse is
emitted as a chirped pulse, carrying the time-reversed replica of the signal (Fig.1).
In this contribution, we study the effects of spectral diffusion and instantaneous spectral
diffusion in Er:YSO on the efficiency and fidelity of our time-reversal protocol.
Figure 1: Example of time-reversal in Er:YSO with a SPE-inspired protocol
[1] T. Böttger, C. W. Thiel, Y. Sun, and R. L. Cone, “Optical decoherence and spectral diffusion at
1.5µm in Er3+:Y2SiO5 versus magnetic field, temperature, and Er3+ concentration”, Phys. Rev. B 73,
075101 (2006).
[2] G. K. Liu and R. L. Cone, “Laser-induced instantaneous spectral diffusion in Tb3+ compounds as
observed in photon-echo experiments”, Phys. Rev. B 41, 6193–6200 (1990).
[3] K. D. Merkel, and W. R. Babbitt. "Chirped-pulse programming of optical coherent transient true-
time delays." Optics Letters 23, 528 (1998).
[4] V. Damon, V. Crozatier, T. Chanelière, J.-L. Le Gouët, and I. Lorgeré, "Broadband photonic
arbitrary waveform generation using a frequency agile laser at 1.5 μm." JOSA B 27: 524 (2010).
[5] V. Crozatier, V. Lavielle, F. Bretenaker, J.-L. Le Gouët, and I. Lorgeré, "High-resolution radio
frequency spectral analysis with photon echo chirp transform in an Er: YSO crystal", IEEE J.
Quantum Electron. 40, 1450 (2004).
[6] H. Linget, L. Morvan, J.-L. Le Gouët and A. Louchet-Chauvet, ‘Time-reversal of optically-carried
radiofrequency signals in the microsecond range”, Opt. Lett. 38, 643 (2013).
37
Mo-14 Spectroscopic investigation of Y2SiO5 codoped with Ce3+
-Pr3+
and Ce3+
-Eu3+
ions for potential quantum computing applications
D. Serrano, Y. Yan, J. Karlsson, L. Rippe and S. Kröll.
Department of Physics, Lund University, Box 118 SE-22100, Lund Sweden
E-mail: [email protected]
Rare-earth doped crystals have been investigated in the last years as serious candidates for the
development of quantum computer hardware [1,2]. In the case of Pr3+
and Eu3+
ions, the qubit
states are represented by two different ground-state hyperfine levels. Generation and
controlled manipulation of the qubit states has already been demonstrated in Y2SiO5 crystals
[2,3] and trivalent cerium has recently been proposed as readout ion for single Pr3+
and/or
Eu3+
qubit states [4,5]. The readout scheme is displayed in Fig. 1:
Fig. 1: A first laser pulse resonant with the | ⟩ | ⟩ optical qubit transition is sent in (a). A qubit ion,
initially at state | ⟩, does not interact with this pulse. Then, pulses resonant with the readout transition
are sent in. After each excitation the readout ion will decay back to its ground state by radiative
emission. In (b), a qubit ion initially at state | ⟩ becomes excited after interaction with the first pulse.
The permanent dipole moment of the excited state of the qubit ion is different from that of the ground
state provoking an energy shift, where R is the distance between the qubit and readout ions,
on the readout ion excited-state so that the transition is no longer resonant with the readout pulses and
no excitation nor luminescence can be detected from the readout ion in this case.
The presence or absence of luminescence from the readout ion provides information about the
qubit initial state. The readout mechanism in Fig.1 requires a short distance between the two
ions involved in order to create a sufficient energy shift for the readout ion excited
state. However, at short ionic distances energy transfers from Ce3+
to Pr3+
can also appear,
quenching the Ce3+
luminescence which would be detrimental for the scheme above. A series
of Ce3+
-Pr3+
and Ce3+
-Eu3+
singly doped and codoped Y2SiO5 crystals are studied here. UV
emission from two Ce3+
sites will be shown and the different energy transfer paths will be
discussed, establishing their efficiency as a function of the ionic distances.
[1] N. Ohlsson et al., Optics Communications 201 (2002) 71–77
[2] J.J. Longdell et al., Phys. Rev. A 69 (2004) 032307
[3] L. Rippe et al., Phys. Rev. A 77 (2008) 022307
[4] J. Wesenberg et al., Phys. Rev. A 75 (2007) 012304
[5] Y. Yan et al., Phys. Rev. B. (2013) Submitted
38
Mo-15 Fluorescence Resonance Energy Transfer Scanning Probe Microscope-
controlled quantum computing using optical transitions in rare-earth ions in crystals
S. K. Sekatskii
Laboratoire de Physique de la Matière Vivante, IPSB, BSP, Ecole Polytechnique Fédérale de
Lausanne, Lausanne, CH 1015, Switzerland
For numerous optical transitions of rare-earth ions in crystals, for the case of liquid helium
temperatures the decoherence (dephasing) time becomes quite comparable with the radiation
decay time. In some cases it can attain the value of a few milliseconds while microsecond
decoherence times are a widespread phenomenon. At such conditions Fluorescence
Resonance Energy Transfer (FRET) process between identical dopant ions is a reversible
coherent process, and the quantum dynamics of the system can be well approximated by a
standard dynamics of a two-level quantum system: the excitation energy flows back and forth
between donor and acceptor. For typical cases, the period of this energy exchange is equal to
the radiation decay time when the donor – acceptor distance is around 20 nm. Hence all the
parameters required are quite feasible with modern Scanning Probe Microscopy (SPM)
technique. Fine adjustment of the spectral lines of different ions can be done using Stark
effect caused by a local electric field of the SPM tip. Dividing the coherent FRET pair
between SPM tip and sample, and starting from the situation when donor is excited while
acceptor is not, one is able, by applying DC voltage pulses onto the SPM tip – carrying
piezocrystal, to prepare desirable quantum states of the donor – acceptor(s) system. We
showed how the multiparticle entangled states, quantum computing C…CNOT operations
(donor remains excited if and only if acceptors were initially excited), etc. can be realized [1].
The first model experiments in the field working with pair centers of neodymium ions in
calcium fluoride crystal (M - centers) have been fulfilled [2]. Ions in these centers resonantly
interact with each other and decoherence time for temperature of T = 8 K is large enough
(accumulated photon echo experiments revealed a value of 6.3 ns). For these M – centers, Bell
entangled states of vacuum and single excitons, as well as of vacuum and biexcitons, were
prepared using the pump-probe laser spectroscopy with tunable nanosecond pulsed lasers. We
analyzed decoherence processes in the system, and showed that 85% fidelity has been
achieved in our experiments. Besides pair centers of neodymium ions in fluoride crystals,
quartet N - centers (Nd ions occupy the vortices of a right tetrahedral) also do exist in fluoride
crystals. They possess much more reach energy structure, which enable to construct more
interesting multiparticle entangled states including e.g. Greenberger – Horne – Zeilinger
vacuum – four-exciton states. New experiments with these and other suitable crystals [3] are
planned [4, 5] having in mind unique helium temperature SNOM recently constructed in the
Cryogenic department of P.N. Lebedev Physical Institute RAS [6], and corresponding
perspectives also will be discussed.
[1] S. K. Sekatskii, M. Chergui and G. Dietler, Europhys. Lett. 63, 21 (2003).
[2] S. K. Sekatskii, T.T. Basiev, I. T. Basieva et al., Opt. Communicat. 259, 298 (2006).
[3] E. P. Chukalina, M. N. Popova, S. L. Korableva, R. Yu. Abdulsabirov, Phys. Lett. A 269,
348 (2000).
[4] I. T. Basieva, T. T. Basiev, G. Dietler et al., Phys. Rev. B74, 165329 (2006).
[5] T. T. Basiev, I. T. Basieva, A. A. Kornienko et al., J. Mod. Opt. 59, 166 (2012).
[6] M. G. Petrova, G. V. Mishakov, E. I. Demikhov, A. I. Sharkov, Bull. Lebedev Phys. Inst.,
37, 276 (2010).
39
TuI-1 Optical properties of strain- and composition tuned RNiO3
J. Ruppen, J. Teyssier, A. Georges, J.-M. Triscone, D. van der Marel
Département de Physique de la Matière Condensée Université de Genève
Rare-earth nickelates with the composition RNiO3 where R is a trivalent rare earth ion, are
among the few perovskite oxides showing a very sharp Metal-Insulator (MI) and a low
temperature antiferromagnetic ordering. The energy scale of both MI and magnetic transitions
can be tuned by the nature of the rare-earth, the doping or the strain applied thought the lattice
mismatch between the substrate and the film. Using the technique of epitaxial thin film
growth, it is possible to stabilize nickel in the trivalent state corresponding to RNiO3. Using
spectroscopic ellipsometry in the visible range and transmission and reflectivity in the
infrared, we extracted the temperature dependence of the optical conductivity of films of
varying composition and strain. The spectra show unusually clear and strong signatures of a
redistribution of free carrier low energy spectral weight to high energy, on the order of 1 eV
and higher. This gives very rich information on the reconstruction of the electronic structure
across the transition.
40
TuI-2 Orbitons and orbital correlations in RVO3 studied by RIXS and optics
M. Grüninger, J. Reul, L. Fels
II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
E-mail: [email protected]
The 3d2 vanadates RVO3 (R = Y or rare earth) display a variety of orbitally and magnetically
ordered states, and orbital exchange interactions as well as orbital fluctuations are expected to
be strong. We have studied the orbital excitations via RIXS and infrared absorption, and
investigated the orbital correlations via ellipsometry.
Using high-resolution RIXS we aim at the first unambiguous observation of a novel kind of
elementary excitations in a solid, namely orbitons, propagating orbital excitations. The
experimental proof for the existence of low-energy orbitons is still lacking. Typically,
superexchange is assumed to be the driving force for the propagation of orbitons, whereas the
coupling to the lattice is supposed to suppress the dispersion. We have observed orbital
excitations in YVO3 and GdVO3 at the V L edge and the O K edge. Due to the excellent
resolution of 60 meV, we have been able to resolve two different features at low energies,
which we interpret as one-orbiton and two-orbiton excitations. For both features, the results
are in good agreement with infrared absorption data. In RIXS, the one-orbiton peak displays a
clear momentum dependence. We discuss whether this reflects a matrix-element effect or the
sought-after dispersion. The two-orbiton excitation is attributed to the exchange of orbitals
between adjacent sites. These results establish that both superexchange and the coupling to
the lattice are relevant for a quantitative understanding of the orbital excitations in RVO3.
Using ellipsometry, we study the excitations from the lower to the upper Hubbard band [1].
We obtain a consistent description of the multi-peak structure in terms of the different d3
multiplets, solving the discrepancy between different data sets reported in the literature. The
optical spectral weight of the different absorption peaks shows a strong temperature
dependence, which reflects nearest-neighbor spin-spin and orbital-orbital correlations. A
comparison of our data with theoretical predictions based on either 'classical' orbital order or
strong orbital fluctuations shows that the latter can be ruled out.
[1] J. Reul, A.A. Nugroho, T.T.M. Palstra, and M. Grüninger, Phys. Rev. B 86, 125128
(2012).
41
TuI-3 Charge transfer transitions in optical absorption and luminescence of NiO
A. S. Moskvin
Ural Federal University, 620083, Ekaterinburg, Russia
Nickel monoxide NiO with its rather simple rocksalt structure, a large insulating gap and an
antiferromagnetic ordering temperature of TN =523K has been attracting many physicists as a
prototype strongly correlated oxide. However, despite several decades of studies there is still
no consensus on the detailed electronic structure of NiO and comprehensive assignment of
different spectral features. Our extensive studies of the optical response of many 3d oxides
(see, e.g., [1] and references therein) have shown that reliable semiquantitative predictions
can be made in frames of a simple cluster approach. The technique provides a clear physical
picture of the complex electronic structure and the energy spectrum, as well as the possibility
of a quantitative modeling. In a certain sense the cluster calculations might provide a better
description of the overall electronic structure of insulating 3d oxides than the band structure
calculations. Starting with octahedral NiO6 cluster with the point symmetry group Oh we deal
with five Ni 3d and eighteen oxygen O2p atomic orbitals forming both hybrid Ni 3d-O 2p
bonding and antibonding eg and t2g molecular orbitals (MO), and purely oxygen nonbonding
a1g(σ), t1g(π), t1u(σ), t1u(π), and t2u(π) orbitals. The onset of p-d charge transfer (CT) bands in
NiO is argued to be related with the dipole-forbidden t1g(π)→eg, or 3A2g→
1,3T1g,
1,3T2g
transitions near 3.7 eV, then these include two formally dipole-allowed so-called π→σ p-d CT
transitions, weak t2u(π)→eg, and relatively strong t1u(π)→eg CT transitions, respectively, each
giving rise to 3A2g→
3T2u transitions [2,3]. Finally main p-d CT band is ended by the strongest
dipole-allowed σ→σ t1u(σ)→eg (3A2g→
3T2u) CT transition around 7 eV [2,3]. Strong dipole-
allowed Franck-Condon d(eg)-d(eg) CT transition manifests itself in NiO as a strong spectral
feature near 4.5 eV. This Mott transition is related with the σ−σ-type eg−eg charge transfer
t2g6eg
2+ t2g
6eg
2→ t2g
6eg
3+ t2g
6eg
1, or anti-Jahn-Teller
3A2g +
3A2g→
2Eg +
2Eg transition between
nnn Ni sites with the creation of electron [NiO6]11−
and hole [NiO6]9−
centers (nominally Ni+
and Ni3+
ions) thus forming a bound electron-hole dimer, or d-d CT exciton prone to be self-
trapped in the lattice due to electron-hole attraction and strong ”double” Jahn-Teller effect for
the both electron and hole centers. We have shown [2] that a recombination transition in the
self-trapped d-d CT exciton does nicely explain the XUV excited bulk luminescence of NiO
with puzzling well isolated doublet of very narrow lines with close energies near 3.3 eV [2].
To the best of our knowledge it is the first observation of the self-trapping and luminescence
for the d-d CT excitons. The time resolved luminescence measurements along with the
absorption and reflectance spectra are shown to be an instructive tool for elucidation of the p-
d and d-d CT excitations and their relaxation in 3d oxides [2].
The work was partially supported by the RFBR Grant N° 12-02-01039.
[1] A.S. Moskvin, R.V. Pisarev, Low Temp. Phys. 36, 489 (2010); A.S. Moskvin, Optics
and Spectroscopy, 111, 403 (2011).
[2] V.I. Sokolov et al., JETP Letters, 95, 528 (2012); Phys. Rev. B 86, 115128 (2012).
[3] V I Sokolov et al., Low-energy charge transfer excitations in NiO, IOP Conference
Series: Materials Science and Engineering, 38, 012007 (2012).
42
TuI-4 Temperature influence on the narrow lines I1 and I2 in Ni0.6Zn0.4O X-ray
excited luminescence spectrum
V. I. Sokolov1)
, V. A. Pustovarov2)
,V. Yu. Ivanov2)
, S. I. Omelkov2)
, V. N. Churmanov2)
,
N. B. Gruzdev1)
, P. S. Sokolov3)
, A. N. Baranov3)
1 Institute of Metal Physics UB RAS, 620990, S. Kovalevskaya str. 18, Ekaterinburg, Russia
2 Ural Federal University, 620002, Mira str. 19, Ekaterinburg, Russia
3 Lomonosov Moscow State University, 119991, Moscow, Russia
Investigation of energy spectrum of 3d-transition metal oxides is the actual problem of the
condensed matter physics. Experimental researches of interband transitions in NiO and CoO
oxides were realized by the methods of optical spectroscopy and inelastic X-ray scattering.
Recently the interesting results were achieved in connection with the observation of
photoluminescence (PL) and photoluminescence excitation (PLE) spectra of NixZn1-xO solid
solutions using X-ray ultraviolet (XUV) radiation (BW3 beamline; DESY, Hamburg) . It
turned out that at the temperature of 8 K in the luminescence spectrum with the excitation of
130 eV narrow lines I1 and I2 were observed at the energies of 3.339 eV and 3.393 eV
respectively [1,2]. The most intensive lines have been registered for the composition of
Ni0.6Zn0.4O. For this solid solution the narrow
lines I1 and I2 were investigated in this paper in
the temperature region of (8 – 50) K.
Fig. 1. X-ray luminescence spectra (fast component) of
Ni0.6Zn0.4O at the temperature of 30 K (1) and 8 K (2).
Excitation energy Eexc=130 eV
Fig. 1 represents narrow lines I1 and I2 for the
temperatures of 8 and 30 K. It is well seen that at
the increasing temperature the relation of
maximal intensities of the lines change. At 8 K
the relation of the lines' intensities I2/I1 is somewhat more than 2, at 30 K the intensities
become equal. The line I2 shifts towards low energies approximately by 7.5 meV. The shifting
of this line is -0.35 meV/K. The shifting of the line I1 is significantly less. The intensities
decay with the time of 10 ns and 1 ns correspondingly. This lets us assume that the lines I1
and I2 may have different natures. The papers [1,2] discussed two versions of emergence of
the lines I1 and I2 : self trapping of p-d and d-d charge transfer exciton annihilation. The
version of radiative recombination of self trapped d-d excitons was adopted as the most
possible. Taking into account the shifting of the line I2 (-0.35 meV/K) and the edge of p-d
transitions at the temperature lowering from 300 K to 90 K received for thin films NiO on
CaF2 substrate (-0.42 meV/K) and on quartz substrate (-0.29 meV/K) we can assume that the
line I2 arises due to p-d exciton annihilation. For the final conclusion a detailed investigation
of the absorption edge in NiO at low temperatures is required by the methods of absorption
and electroabsorption.
The work was partially supported by the Ural Branch of RAS (grant 12-u-2-1030).
[1] V.I. Sokolov, V.A. Pustovarov, V.N. Churmanov, V.Yu. Ivanov, N.B. Gruzdev,
P.S. Sokolov, A.N. Baranov, A.S. Moskvin, Pis'ma v ZhETF 95(10), pp. 595-600, (2012)
[2] V.I. Sokolov, V.A. Pustovarov, V.N. Churmanov, V.Yu. Ivanov, N.B. Gruzdev, P.S.
Sokolov, A.N. Baranov, A.S. Moskvin, Phys. Rev. B 86, 115128 (2012)
[3] C.E. Rossi, W. Paul, J. Phys. Chem. Solids. 30 (1969) 2295-2305
3,30 3,32 3,34 3,36 3,38 3,40 3,42 3,440,0
0,2
0,4
0,6
0,8
1,0
Inte
ns
ity
, a
rb.u
nit
s
Photon energy , eV
21
43
TuI-5 Electron-phonon interaction in the hyperkagome lattice iridates
D. Pröpper1)
, A. N.Yaresko1)
, T. Larkin1)
, T. Takayama2)
, H. Takagi1,2)
, B. Keimer1)
,
A. V. Boris1)
1)
Max-Planck-Institut für Festkörperforschung, Heisenbergstr.1, D-70569 Stuttgart, Germany
2) Department of Advanced Materials, University of Tokyo, Kashiwa 277-8561, Japan
Na3Ir3O8 is a metallic counterpart of the geometrically frustrated antiferromagnet Na4Ir3O8
[1]. Both compounds have a cubic structure with the iridium sites which form a three-
dimensional hyperkagome lattice of corner-sharing triangles. We report the complex dielectric
function of high-quality Na3Ir3O8 single crystals determined by spectroscopic ellipsometry in
the wide spectral range of 10 meV - 6.5 eV. The far-infrared phonon spectra exhibit highly
asymmetric line shapes characteristic of Fano resonances. With decreasing temperature, we
observe a sharp increase of the infrared intensity of the Fano-shaped phonon modes followed
by concomitant changes in the low energy electronic background, formed by electronic
transitions between Ir 5d t2g bands mostly of Jeff
=5/2 character. The observed infrared
anomalies are discussed in the framework of quantum Fano interference effects between
discrete phonons and continuous electron-hole pair excitations. The role of complex
hyperkagome lattice structure and strong spin-orbit coupling is considered.
[1] Y. Okamoto et al., Phys. Rev. Lett., 99, 137207 (2007)
44
TuI-6 Magnetic order and excitations in iridium oxides
Giniyat Khaliullin
Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569, Stuttgart,
Germany
E-mail: [email protected]
In 5d transition metal compounds such as iridium oxides, large spin-orbit coupling entangles
the spin and orbital subspaces and may lead to unusual interactions and ground states. In this
talk, after some basic introduction to the iridates, the following topics will be addressed: (i)
Magnetic ordering and excitations in single layer Sr2IrO4 [1,2,3] and bilayer Sr3Ir2O7 [4,5]
iridium perovskites; (ii) Exchange interactions in a hexagonal lattice iridates, Kitaev-
Heisenberg model, its phase diagram including spin-liquid states [1,6]; (iii) origin of the
zigzag magnetic order and spin waves in Na2IrO3 [7].
[1] G. Jackeli and G. Khaliullin, Phys. Rev. Lett. 102, 017205 (2009).
[2] Jungho Kim et al., Phys. Rev. Lett. 108, 177003 (2012).
[3] B.H. Kim, G. Khaliullin, and B.I. Min, Phys. Rev. Lett. 109, 167205 (2012).
[4] J.W. Kim et al., Phys. Rev. Lett. 109, 037204 (2012).
[5] Jungho Kim et al., Phys. Rev. Lett. 109, 157402 (2012).
[6] J. Chaloupka, G. Jackeli, and G. Khaliullin, Phys. Rev. Lett. 105, 027204 (2010).
[7] J. Chaloupka, G. Jackeli, and G. Khaliullin, Phys. Rev. Lett. 110, 097204 (2013).
45
TuI-7 Sub-THz spectroscopy of the layered manganite LaSrMnO4
in ultra-strong magnetic fields
V. Kataev
Leibniz Institute for Solid State and Materials Research IFW Dresden, 01069 Dresden,
Germany
E-mail: [email protected]
In this talk high-field ESR (HF-ESR) and a very peculiar anomalous magnetic field driven
absorption of sub-THz radiation in the single layer manganite La1Sr1MnO4 (LSMO) in
magnetic fields up to 40 T will be discussed
The LSMO crystallizes in the K2NiF4-tetragonal structure type. The Mn3+
O2-
-octahedra are
strongly elongated along the tetragonal c-axis implying that at all Mn(3d4)-sites the 3z
2-r
2
orbital from the eg set is occupied. This ferro-orbital order completes with the collinear C-type
antiferromagetic order at TN = 127 K. There is however a growing number of observations
suggesting that the physics of LSMO is not confined to the spin sector only. Remarkably,
LSMO shows anisotropic anomalies in the thermal expansion indicating a T-dependent
redistribution of the electron density between the eg orbitals, i.e. that the orbital degrees of
freedoms are not completely quenched. Furthermore, the observation of small ferromagnetic
moments in SR and magnetization experiments is incompatible with the collinear spin
structure and the completed ferro-orbital order.
Indeed, our HF-ESR measurements of a high-quality single crystal of LSMO in the
paramagnetic regime at T > TN reveal a specific T-dependence of the g-factors and the single-
ion anisotropy gap which gives evidence for a progressive occupation of the out-of-plane
3z2-r
2 orbital with lowering T. At the magnetic phase transition a well-defined ESR signal
transforms into extremely broad field dependent absorption bands with very peculiar
properties. In particular, at T << TN, with increasing the magnetic field strength B above 15 T
the transmission signal Tr(B) strongly reduces and exhibits a non-monotonous frequency
dependence in a range 90 GHz < < 1.2 THz. A broad step in Tr(B) shows a strong
hysteresis for B || c-axis but is reversible for the B c geometry. Though LSMO nominally
contains no holes we have found a significant negative magnetoresistance at T < TN in
magnetic fields up to 30 T. The unusual field driven microwave absorption in LSMO bears
striking similarity with the B-dependence of the dielectric constants found in the multiferroic
manganites GdMnO3 and TbMnO3 and presented as a possible evidence for electromagnons.
Our observations may indicate that a dynamic interplay between spins, orbitals and charges is
not exceptional for the pseudocubic perovskites but may also occur in the layered manganites
such as LSMO.
This work has been done in collaboration with U. Schaufuß, B. Büchner (IFW Dresden), R.
Klingeler (Kirchhoff Institute for Physics, University of Heidelberg, Heidelberg), M. Goiran,
B. Raquet, H. Rakoto, J.-M. Broto (Laboratoire National des Champs Magnétiques Pulsés,
Toulouse), P. Reutler and A. Revcolevschi (Laboratoire de Chimie des Solides, Université
Paris-Sud, Orsay)
46
TuI-8 NMR/NQR evidence for charge and orbital order of cobalt ions in NaxCoO2
I. R. Mukhamedshin1,2
, H. Alloul2)
1)
Institute of Physics, Kazan Federal University, Kazan, 420008, Russia, 2)
Laboratoire de Physique des Solides, Université Paris-Sud, Orsay, 91405, France
E-mail: [email protected]
The sodium cobaltates NaxCoO2 are layered oxyde materials somewhat similar to the
cuprates in as much as the charge doping of the CoO2 layers is controlled on a large range by
variation of the Na content. The significant difference of cobaltates with the cuprates is that
the Co of the CoO2 plane are ordered on a triangular lattice and not on a square lattice as for
the CuO2 plane of the cuprates. A rich variety of physical properties ranging from ordered
magnetic states, large thermoelectric effect, high Curie-Weiss magnetism and metal insulator
transition, superconductivity etc have been observed in the cobaltates.
While many experiments and theoretical calculations have considered that in sodium
cobaltates the Co magnetism is uniform, NMR/NQR experiments and structural investigations
have given evidence that for x≥0.5 a large interplay occurs between atomic arrangements of
Na ions and electronic properties of CoO2 planes [1]. In this talk we demonstrate that
NMR/NQR is a powerful technique allowing us to establish reliably the relation between the
local Na order, the actual Na content, and the local magnetic properties of the studied samples
[2,3]. The incidence of the structural order on the charge disproportionation and on the
physical properties of sodium cobaltates will also be discussed.
This work was partially supported by the Ministry of Education and Science of the
Russian Federation (Budget Theme No. 12-24 and Project No. 2010-218-01-192).
[1] H.Alloul, I.R.Mukhamedshin, G.Collin, N.Blanchard, EPL 82, 17002 (2008).
[2] I.R.Mukhamedshin and H.Alloul, Phys. Rev. B 84, 155112 (2011).
[3] H.Alloul, I.R.Mukhamedshin, et al., Phys. Rev. B 85, 134433 (2012).
47
TuI-9 Low-lying excitations in the orbitally active A-site spinels
FeSc2S4, FeCr2O4, and FeCr2S4
J. Deisenhofer1)
, M. Schmidt1)
, Z. Wang1)
, V. Tsurkan1,2)
, A. Loidl1)
1) Experimental Physics V, Center for Electronic Correlations and Magnetism, University of
Augsburg, D-86135 Augsburg, Germany 2)
Institute of Applied Physics, Academy of Sciences of Moldova, MD-2028~Chisinau,
Republic of Moldova
We investigated the low-lying excitations of the spinels FeSc2S4, FeCr2O4, and FeCr2S4 by
THz spectroscopy. FeSc2S4 reportedly is in a spin-orbital singlet ground state [1,2], while the
other two compounds exhibit complex magnetically ordered ground states and orbital
ordering transitions [3]. In all compounds we observed excitations which we assign to
transitions related to the electron excitations of Fe2+
ions in tetrahedral environment. We will
discuss the evolution of these excitations in the case of the orbital-ordering transition in
FeCr2S4 and the competition of spin-orbit coupling and Jahn-Teller interaction as a source for
orbital frustration in these systems.
[1] A. Krimmel et al. Phys. Rev. Lett. 94, 237402 (2005).
[2] G. Chen et al. Phys. Rev. Lett. 102, 096406 (2009)
[3] V. Tsurkan et al., Phys. Rev. B 81, 184426 (2010).
48
TuI-10 Specific electronic and vibronic structures in optical spectra
of copper metaborate CuB2O4
K. N. Boldyrev1)
, M. N. Popova1)
, L. N. Bezmaternykh2)
, R. V. Pisarev3)
1Institute of Spectroscopy, Russian Academy of Sciences, 142190, Troitsk, Moscow, Russia
2Kirenskii Institute of Physics, SB Russian Academy of Sciences, 660036, Krasnoyarsk,
Russia 3Ioffe Physical-Technical Institute, Russian Academy of Sciences, 199034, St. Petersburg,
Russia
Copper metaborate CuB2O4 has a complex crystal structure (S.G. I42d, Z=12) with two
different (4b and 8d) crystallographic positions for the magnetic Cu2+
ions (S=1/2), which
define its unique properties. Intra- and inter-atomic interactions within the Cu2+
sublattices
lead to an antiferromagnetic ordering below TN1=21 K, rich magnetic phase diagram,
commensurate and incommensurate structures, and phase transitions. Low-temperature
studies of CuB2O4 have revealed quite unique electronic spectra which were attributed to the
narrow zero-phonon (ZP) lines related to d-d electronic transitions in the 4b and 8d sites,
accompanied by an extremely rich vibronic structure consisting of up to 40 and more phonon
sidebands for each ZP line [1].
It was obvious that for the understanding of this complex vibronic structure, information on
phonon spectra is an absolutely necessary prerequisite. In this work, we have performed a
complex study of the lattice dynamic of CuB2O4. Reflection, transmission and Raman back-
scattering spectra were measured. Analysis of the spectra and ab initio DFT calculations
allowed us to reliably identify and to define the parameters of 73 from 75 optically active
phonons of the Brillouin zone center. We show that some groups of phonons can be
interpreted within the framework of the Davydov splitting of the intra-molecular vibrations of
the CuO4 complex. It was found that the frequencies of phonon modes are weakly dependent
on temperature, indicating either negligible or vanishing magnitude of the magneto-elastic
interactions.
Using the experimentally found frequencies for the ZP lines attributed to particular electronic
transitions from the ground (x2-y
2) state to the (xy), (xz,yz), and (z
2) states, we have calculated
the genuine cubic crystal field parameter Dq and tetragonal parameters Ds and Dt for the Cu2+
ions in both sublattices [1]. Using these parameters as the reference values, we estimated Dq,
Ds, and Dt for several other cuprates with different Cu-O bond lengths. In particular, the
splitting of the 3d states in La2CuO4, Nd2CuO4, CuGeO3, and in some other cuprates was
analyzed.
Contrary to a rigid behavior of phonon frequencies with respect to temperature and magnetic
transitions, we found that the ZP lines originating from the Cu2+
(4b) ions clearly correlate in
their behavior (spectral width and position) with an antiferromagnetic ordering at TN1=21 K
while those coming from the Cu2+
(8d) ions correlate with TN2=9.5 K. However, small
peculiarities in the behavior of Cu2+
(4b) lines at TN2 and Cu2+
(8d) lines at TN1 were observed
which indicate the mutual influence of the two magnetic subsystems.
This work is supported by Programs of the Russian Academy of Sciences, the Ministry of
Education and Science, and the Russian Foundation for Basic Research.
[1] R. V. Pisarev, A. M. Kalashnikova, O. Schöps, et al., Phys. Rev. B 84, 075160 (2011).
[2] R. V. Pisarev, K. N. Boldyrev , M. N. Popova, et al., Phys. Rev. B (submitted).
49
TuI-11 Boson peak in overdoped manganites La1-xCaxMnO3
L. S. Kadyrov1,2)
, B. Gorshunov1,2,3)
, E. Zhukova1,2,3)
, V. I. Torgashev4)
, E. A. Motovilova1,2)
,
F. Fischgrabe5)
, V. Moshnyaga5)
, T. Zhang6)
, R. Kremer7)
, U. Pracht3)
, S. Zapf3)
, M. Dressel3)
1)
A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, 119991,Vavilov
Str., 38, Moscow, Russia E-mail: [email protected]
2)Moscow Institute of Physics and Technology (State University), 141700, Institutskiy
Pereulok, 9, Dolgoprudny, Russia 3)
1. Physikalisches Institut, Universität Stuttgart, 70550, Pfaffenwaldring 57, Stuttgart,
Germany 4)
Faculty of Physics, Southern Federal University, 344090, Rostov-on-Don, Russia 5)
I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077, Friedrich-Hund-
Platz, 1, Göttingen, Germany 6)
Key Laboratory of Materials Physics, Institute of Solid State Physics,
Chinese Academy of Sciences, 230031, Hefei, People’s Republic of China 7)
Max-Planck-Institut für Festkörperforschung, 70569, Heisenbergstrasse 1, Stuttgart,
Germany
Spectra of optical conductivity and dielectric permittivity of strongly doped manganites
La1−xCaxMnO3 (x≥0.5) (ceramic samples) are measured at terahertz and infrared frequencies
and at temperatures 5 K to 300 K. In the charge-ordered phase for commensurate x values
absorption lines are detected in the terahertz spectral range right below the charge-ordering
temperature. It is shown that these lines cannot originate from charge-density wave
condensate but are rather connected with acoustic phonons that become optically active by
folding of the Brillouin zone. At lower temperatures a strongly asymmetric extra absorption
band develops at frequencies corresponding to the position of the lowest-energy van Hove
singularity in the reduced Brillouin zone. The band is assigned to the boson peak, i.e. to the
excess of lattice vibrational states over the standard Debye contribution. The folded phonons
and the boson peak do not show up for incommensurate calcium contents when no distinct
Brillouin zone folding exists.
10 100 60010
-1
100
101
102
5
180 K
Optica
l con
du
ctivity (
-1cm
-1)
Wavenumber (cm-1)
280 K
5 K
220 K
5
10 20 400
10
20
(
-1cm
-1)
(cm-1)
T = 5 K
Fig.1. Temperature dependence of the optical conductivity spectra of La1/3Ca2/3MnO3 ceramic
sample. The arrow indicates the vibrational acoustic modes that become infrared active by
Brillouin zone folding due to charge ordering. The inset demonstrates that it is not possible to fit
the low-frequency asymmetrical band by a Lorentzian curve (dashed line).
50
TuI-12 Mixed valence pair center Cr2+
-Cr3+
in KZnF3 crystal:
EPR and optical studies
D. G. Zverev1)
, L. R. Giliazov1)
, G. S. Shakurov2)
, V. F. Tarasov 2)
, S. I. Nikitin1)
1 Kazan Federal University, Kremlevskaya 18, Kazan, Russia
2 Kazan Physical Technical Institute, Sibirsky Trakt 10-7, Kazan, Russia
In the optical absorption spectra of KZnF3:Cr3+
,Cr2+
crystals the absorption lines of the
mixed valence pair centres Cr3+Cr
2+ have been observed [1]. The intensity of these lines was
proportional to the product of the Cr2+
and Cr3+
concentrations. Optical studies with an
applied electric field and uniaxial stress have shown that the symmetry of the pair centre is
tetragonal, the excess charge compensation of the Cr3+
ion of the pair centre is not local and
the eg-electron of the pair centre is significantly localized due to the strong vibronic
interaction. The only possible way of the local charge compensation that maintains the
tetragonal symmetry is a defect located on the axis of the pair centre (e.g. the vacancy in the
nearest Zn2+
site). As this variant of the charge compensation has no advantage with respect to
the other ones it was proposed that the charge compensation is nonlocal. However, it is also
possible that the influence of the crystal lattice distortion caused by the possible local charge
compensation mechanisms is much smaller than the axial component of the crystal field along
the pair axis and doesn’t modify significantly the polarization properties of the absorption
lines of the pair centre. To clarify the microscopic structure of the pair EPR spectroscopy can
be very useful.
Measurements of EPR spectra were performed in the standard X- and Q-microwave
bands and in a wide submillimetre range of 79-535 GHz with the home-built quasi-optical
EPR spectrometer. In the EPR spectra of the KZnF3:Cr3+
, Cr2+
crystal, besides the well-
understood signals of the single Cr3+
and Cr2+
ions, the resonance lines originating from the
mixed valence pair centres Cr3+
–Cr2+
were identified. It was found that the total spin S=7/2 is
the ground state of the centre which testified the ferromagnetic character of the exchange
interaction. The structure of the EPR spectrum reveals the hyperfine interaction of the centre
with two equivalent 19
F nuclei with the corresponding splitting reduced with respect to that of
the single Cr2+
ion. The reduction factor value ~2/7 indicates the “strong exchange” limit in
the Cr2+Cr
3+ pair centre. The exchange integral value is J = 471 GHz (15.7 cm
-1) and fine
structure parameter D(Cr2+
) = 78.2 GHz were found. The value of the exchange integral is in
the good agreement with that obtained from the optical spectroscopy data and the fine
structure parameter is similar to the one of the single Cr2+
ion.
Besides the observation of the purely tetragonal symmetry pair centre, in EPR
spectrum angular dependencies the monoclinic symmetry centre with the axes close to the C4
axes of the crystal and fine structure parameters similar to the pair centre was found. Angular
dependence of the EPR lines positions for this centre is described well within an assumption
of the local charge compensation of the Cr3+
by the vacancy in the nearest K+ ion site.
Observation of the monoclinic-symmetry pair centre together with the tetragonal one verifies
the possibility of both the local and nonlocal charge compensation mechanisms. Structure of
the EPR spectra in the submillimetre range were satisfactorily explained in this model also.
[1] M.V.Eremin, S.I.Nikitin, S.Y.Prosvirnin, N.I.Silkin, R.V.Yusupov, Solid State Commun.
117, 297 (2001).
51
TuI-13 High-frequency EPR of Fe3+
dimers in α-Al2O3
G. S. Shakurov, S. A. Migachev
Kazan Physical Technical Institute, 420029, Sibirsky trakt 10/7, Kazan, Russia.
At the present time corundum (α-Al2O3) has many applications in science and technology.
The crystals with Fe3+
ions are used for sapphire masers [1]. Although spectroscopic
properties of isolated iron ions in corundum well known the pair centers have been
insufficiently studied. The Fe3+
- Fe3+
dimers were studied early by EPR (X-band)
spectroscopy method [2, 3]. Studying the week satellite lines of isolated Fe3+
ions it was
suggested that there are the different types of on- and off-axis Fe3+
- Fe3+
pairs. However due
to overlapping of EPR lines of the isolated and dimer spectra a detailed study of pair centers
was impossible. Available up to date information is contradictory and incomplete.
We used tunable high frequency (37-850 GHz) EPR spectrometer to study the iron pair
centers in Al2O3:Fe crystal separately from isolated ones. Tuning the resonance frequency we
found excited levels of each dimer and investigated their angular and field-frequency
dependencies. All measurements were done at the liquid helium temperature. Magnetic field
up to 9 kG was produced by the usual electromagnet.
Numerous resonant transitions were founded and more than 20 Zero-Field-Splittings (ZFS)
were measured. Field-frequency dependencies show that doublet-doublet, doublet-singlet and
singlet-singlet resonance transitions occur.
The three types of the dimers were observed. First type is axial dimer that had not
magnetically inequivalent spectra (KM=1). The g-values of the EPR lines and the number of
excited levels show that an antiferromagnetic exchange takes place. This conclusion is an
agreement with the previous works [2, 3]. The second type of dimer has KM=3. In the
corundum lattice such magnetic multiplicity may have the pairs with symmetry C1 and C2.
The axes of these dimers form the angles 80.1 and 58.3 degrees with C3 axis respectively.
Great values of the g-factors indicate that the Fe3+
ions are coupled by the ferromagnetic
interaction and the ground level has total spin number S=5. The third type has magnetic
multiplicity equal to 6. This dimer (C1 symmetry) in accordance with the corundum lattice
construction should be inclined at the angle of 51.7 degree in relation to the trigonal axis. In
this case also ferromagnetic exchange takes place.
There was also the group of EPR lines that had small signal-to-noise ratio to explore their
angular dependence and to determine their origin. Besides in crystal there were other
transition ions embedded as the trace elements. In particular we observed singlet-doublet
transitions of V3+
(ZFS= 248 GHz) and Fe2+
(ZFS=111 GHz) ions. EPR spectrum of
vanadium ion had well resolved hyperfine structure. Identification of Fe2+
was done using
known values of g-factor (gc=3.4) and ZFS. One of the transition (ZFS=227 GHz) presumably
is connected with Cr4+
ion.
The obtained experimental data give possibility to build the preliminary energy level structure
of dimers. We identified different types of pair centers and measured their g-factors and ZFS.
For unambiguous theoretical description of the EPR spectra the temperature measurements
are needed using the more pure crystal.
[1] K.Benmessai et al. Phys.Rev. B 87, 094412 (2013)
[2] R.L.Garifullina, M.M.Zaripov, V.G.Stepanov Fizika tverdogo tela 12 55 (1970)
[3] Richard Bramley and May B McCool J. Phys. C: Solid State Physics 9 1793 (1976)
52
TuI-14 Microstructure of the dynamic Mn2+
centres in SrTiO3:
EPR and optical studies
R. V. Yusupov1)
, D. G. Zverev1)
, A. A. Rodionov1)
, S. I. Nikitin1)
, L. R. Gilyazov1)
,
V. A. Trepakov2,3)
, A. Dejneka3)
1) Kazan Federal University, Kremlevskaya 18, Kazan, Russia
2) Ioffe Physical-Technical Institute RAS, 194021 St-Petersburg, Russia
3) Institute of Physics AV CR, Na Slovance 2, 18221, Prague 8, Czech Republic
Strontium titanate SrTiO3 (STO) is a so-called quantum paraelectric in which
dielectric constant increases strongly on cooling down but the ferroelectric phase transition
(PT) in the low-temperature region is inhibited by the dominating quantum statistics.
However, the PT can be induced by the applied electric field, UV-illumination or doping by
suitable impurities. Manganese-doped STO (STO:Mn) is among the materials that are studied
for decades in which new intriguing although sample-dependent dielectric and magnetic
anomalies have been found. Electron paramagnetic resonance (EPR) studies of this material at
the temperatures above 100 K reveal the spectra of cubic Mn4+
and Mn2+
centers, several axial
Mn3+
centers associated with oxygen vacancies, Mn4+
-Mn4+
pairs. An on-going intense
discussion is related to the substitutional position of the Mn2+
ions: whether these species
replace the octahedral Ti4+
or 12-fold-coordinated Sr2+
and whether this impurity is centrally-
symmetric or not.
We report on new results of the X-band (9.6 GHz) EPR and optical studies of the
high-quality Verneuil-grown STO:Mn single crystals from Furuuchi Chemical Corporation.
In the EPR spectra the peculiar transformation of the S = 5/2 Mn-related signal is
observed. While at room temperature and above it reveals an ideal cubic symmetry, on
cooling down this spectrum broadens severely so that it can hardly be identified below 100 K.
We report for the first time an observation of the low-symmetry S = 5/2 Mn-related spectrum
that appears below T ~ 10 K and grows steeply in intensity on further temperature decrease.
We assign this observed S = 5/2 centre spectrum transformation to the transition from the
dynamic to static behaviour. The study of the angular dependence of the low-temperature
spectrum shows that in the static limit this centre has the monoclinic symmetry Cs, with the
principal axis tilted from the [011] quasi-cubic axis by approximately 12 degrees in the (110)
plane. Fine structure parameter values are D = 1480 MHz and E = 116 MHz; principal g-
tensor components are gzz = 2.0036, gxx gyy = 2.0030.
Several models of the possible S = 5/2 Mn-related centre with a possibility of dynamic
behaviour have been considered in the literature [1]. The most suitable ones are the off-centre
Mn2+
ion substituting for Sr2+
, and Mn3+
-O– with Mn
3+ ion in octahedral Ti
4+ position and a
hole at one of the oxygen ions. However, the observation of the Mn2+
ion luminescence
corresponding to the spin-forbidden 4T1
6A1 transition with the maximum at 640 nm and the
lifetime of ~14 ms that was possible only with an intense laser excitation allowed us to assign
the observed in the EPR S = 5/2 Mn-related spectrum to the Mn2+
ion located in the Sr2+
ion
position. Dynamic behaviour can be related to the Mn2+
ion jumps between the equivalent off-
centre positions. Transition to the static state then may occur due to the interaction with the
random strains or local electric fields in the crystal. Off-centre Mn2+
evidently has a large
electric dipole moment and may serve as a source for the dielectric anomalies found in
STO:Mn.
[1] Kvyatkovskii O. Phys. Sol. State 54 1397-1407 (2012).
53
TuI-15 Manifestation of the intermediate monoclinic phase in IR-and Raman spectra
of ferroelastic K3Na(CrO4)2: MnO42-
crystals
Yu. E. Kitaev1)
, T. I. Maksimova1)
, K. Hermanowicz2)
, M. Mączka2)
, J. Hanuza2)
1) Ioffe Physical Technical Institute of RAS, 194021 St. Petersburg, Russia
2) Institute of Low Temperature and Structure Research of PAS, 50-422 Wrocław, Poland
In this report, the temperature-induced phase transitions in K3Na(CrO4)2: MnO42-
ferroelastic crystals were studied using a combination of Raman scattering and IR-absorption
experimental methods. The Raman and IR-spectra were measured in the frequency regions of
intramolecular vibrations of CrO4 complexes (310 – 450 cm-1
) and (840 – 1000 cm-1
) within
the wide temperature range of 4 – 300 K.
The spectra transformation with temperature clearly reveal the appearance of new
pronounced features at two temperatures Tc1 ≈ 230 K and Tc2 ≈ 150 K both in low and high-
frequency parts of the spectra. The band splitting and appearance of new lines at Tc1 and Tc2
were observed in both Raman and IR-spectra. This allows us to suggest that the structural
phase transition between the trigonal (P3 m1) and monoclinic (C2/c) phases, determined in X-
ray experiments [1], is realized in two steps via an intermediate phase.
The group theory analysis performed with the use of the SUBGROUPGRAPH program
of the Bilbao crystallographic server (BCS) [2] shows that only two transition paths via two
intermediate phases (monoclinic C2/m or trigonal P3 c1) are allowed by symmetry. Our
calculations, based on the X-ray structural data [1], using the AMPLIMODES program show
that the lattice distortions are consistent with the P3 m1 → C2/m → C2/c path.
The Raman and IR-spectra of K3Na(CrO4)2 under study were interpreted based on the
phonon symmetry in high-, intermediate- and low-symmetry phases and corresponding
Raman and IR selection rules. The P3 m1 → C2/m transition into intermediate phase
corresponds to lattice distortions without the change of the number of atoms in the unit cell.
Due to the change of the lattice point symmetry 3 m → 2/m, the doubly-degenerated Eg and
Eu modes split into Ag + Bg and Au + Bu modes, respectively. In Raman spectra, it is observed
in the splitting of the 346, 389, and 861 cm-1
Eg - modes (originated from the ν2, ν4, and ν3
internal vibrations of CrO4). In IR-spectra, the transition is manifested in the splitting of the
888.9 cm-1
Eu-mode (originated from the ν3 vibration) into 874.2 и 890.9 cm-1
modes. The
second phase transition C2/m → C2/c leads to the unit cell doubling along the c-axis, which
results in the doubling of the number of vibrations due to the folding of Brillouin zone
boundary phonons. This effect was observed both in Raman and IR spectra.
Thus, the experimental data are in a good agreement with the results of our group
theory analysis.
[1] J.Fabry, T.Breczewski, and G.Madariaga, Acta.Cryst. B 50, 13 (1994).
[2] M. I. Aroyo, A, Kirov, C, Capillas, J. M. Perez-Mato, and A. Wondratschek, Acta
Crystallogr. Section A: Found. Crystallogr. 62, 115 (2006); www. cryst.ehu.es
54
Tu1-16 High-temperature diamondlike silicon-based ferromagnetic
with self-organized superlattice distribution of Mn impurity
E. S. Demidov, E. D. Pavlova, A. I. Bobrov, N. V. Malekhonova, A. A. Tronov
Nizhniy Novgorod State University, Gagarin Avenue 23, Nizhni Novgorod 603950, Russia
J. K. Furdyna [1] to necessity to fill a gap between microelectronics and magnetic electronics
had paid attention in 1988. The first ferromagnetic so-called diluted magnetic semiconductors
(DMS) on basis of compounds II-VI [2, 3] and III-V [4] were synthesized in 90s of last
century. Now there are a lot of publications devoted to epitaxy layers of DMS Ga1-xMnxAs
with atomic fraction of Mn impurity x≈0.05 and perfect crystal structure grown up at low
temperatures ≈250°С by molecular beam epitaxy (MBE). However maximum attained Curie
point of this ferromagnetic Ga1-xMnxAs 170 К is below room temperature [5]. Especially
interesting DMS is on basis of elementary silicon semiconductor because of it compatibility
with the most widespread silicon technology. Earlier [6, 7], the mainly investigated in our
laboratory DMS Si:Mn with 10-15 % Mn, synthesized by deposition from laser plasma, has
relatively great mobility of current carriers, the Mn impurity in it shows high electric and
magnetic activity. The ferromagnetism of the DMS was confirmed by observation of
ferromagnetic resonance, abnormal Hall effect, negative magnetoresistance, hysteresis
magnetization and magnetooptic Kerr effect. Recently [8], the crystal structure of this high-
temperature Si:Mn DMS with Curie temperature up to 500 К, deposited from laser plasma on
GaAs(100) substrates at 300°C, was investigated by high-resolution transmission electronic
microscopy and diffraction. This laser technology allows to reach of solid solution of 15%Mn
in silicon with high electrical and full magnetic activity, conservation of diamondlike crystal
structure and epitaxy growth of Si:Mn. The self-organized formation of superlattice structures
takes place with period equal to trebled distance between nearest atomic layers (110) and
interval between layers (110) which are doped by Mn atoms and oriented along direction of
growth of 50 nm Si:Mn film. In this work data of highly resolving electronic microscopy of
such layers in-plane in a direction <100> are presented. It is shown, that really impurity of
manganese atoms is distributed periodically in type (110) planes. As well as earlier [8]
presence of a superlattice with the trebled period is confirmed by data of electronic
diffraction, but in a direction <100>. The structure of films consists from ≈50 nanometers of
domains with relative perpendicular orientation of superlattices. So the possibility of epitaxial
growth of high-temperature silicon ferromagnetic layers with earlier unknown diamond like
structure and self-organized superlattice distribution of manganese impurity is shown.
Authors are grateful to D.A. Pavlov for useful discussion.
[1] J. K. Furdyna, J. Appl. Phys. 64, R29 (1988).
[2] H. Ohno et al., Phys. Rev. Lett. 68, 2664 (1992).
[3] H. Ohno et al., Appl. Phys. Lett. 69, 363 (1996).
[4] H. Munekata et al , Phys. Rev. Lett. 63, 1849 (1989).
[5] Maciej Sawicki, in Spintronic Materials and Technology, Series in Materials Science and
Engineering, ed. By Y.B. Xu, S.M. Thompson, CRC Press Taylor & Francis Group, 2007,
P. 57-76.
[6] E.S. Demidov et al., JETP Lett. 83, 568 (2006).
[7] E.S. Demidov et al. , JETP 106, 110 (2008).
[8] E.S. Demidov, E.D. Pavlova, A.I. Bobrov, JETP Lett. 96, 706 (2012).
55
TuI-17 Luminescent cationic and anionic species in sodalites
M. Lezhnina1,2)
, U. Kynast1)
1) University of Applied Sciences Muenster, Department of Chemical Engineering, Applied
Materials Sciences, 48565, Stegerwaldstr.39, Steinfurt, Germany 2)
On leave from Volga State University of Technology, Department of Physics , 424000,
Lenin-pl.3, Yoshkar-Ola, Russia
Sodalites belong to the feldspathoid class of minerals and are the first and “smallest”
representatives of a series of microporous materials known as zeolites. They have a chemical
and thermal stability superior to other zeolites; moreover, albeit small in diameter (app. 0.6
nm), they provide hospitable shelter voids for numerous optically active organic and
inorganic species. A generalized composition of natural sodalites may be represented as
M8[TO2]12X2, where M = Na+ or (and) Ca
2+; T = Al
3+, Si
4+; X = OH
-, Cl
-, SO4
2-, S
2-. A
simplified sketch of the sodalite structure is shown in fig. 1. Elaborate syntheses permit
substitutions, both on cationic as well as anionic sites. Different astonishing species like the
S3•- radical anion in the well-known ultramarine, for example [1], or other reactive species,
like BH4- and BF4
- anions [2,3], have thus been stabilized in the sodalite cages.
Insertion of “heavy” tetrahedral transition metalate anions (MoO42-
, WO42-
) enables
luminescent processes from rare earth doped sodalites not only in the UV- and visible range
(Eu3+
, Tb3+
), but also the involvement of NIR states. In case of Nd3+
, fairly efficient emission
at 1063 nm was obtained [4], while Yb3+
/Ho3+
and Yb3+
/Er3+
couples led to upconverted
emission in the visible on excitation with a 980 nm laser diode.
The luminescent properties of Eu2+
ions (unfortunately not analogous to transition metalates)
were studied in strontium alumina sodalites with SO42-
and S2-
as counter anions. Efficient
blue emission of anionic S2-
species (quantum yield ca. 50 %) was obtained even in the
absence of rare earth activators, while in the presence of Eu2+
a simultaneous red emission,
reminiscent of SrS:Eu2+
, was observed (fig. 1).
[1] F. Seel, in Studies in Inorganic Chemistry, Vol. 5 (Eds: A. Müller, B. Krebs), Elsevier,
Amsterdam, 1984, pp. 67–89.
[2] J.-Ch. Buhl, T. M. Gesing, C.H. Rüscher, Microporous Mesoporous Mater., 80 (2005) 57.
[3] M.M. Lezhnina, E. Jordan, S.A. Klimin, J. Löns, H. Koller, B.N. Mavrin, U. Kynast, Z. Anorg.
Allg. Chem., 635 (2009) 450.
[4] M. Lezhnina, F. Laeri, L. Benmouhadi, U.Kynast, Adv. Mater. 18 (2006) 280.
250 300 350 400 450 500 550 600 650 7000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.0
0.2
0.4
0.6
0.8
Re
lative
In
ten
sity,
a.u
.
Wavelength, nm
Re
flecta
nce
S2-
Eu2+
Figure 1. Simplified sketch of sodalite structure (on the left) and luminescence spectra (on the right)
of Sr8Al12O24(SO4, S)2 sodalite doped with Eu2+.
56
TuI-18 Electron Dynamics in Single- and Few-Layer MoS2
Christoph Gadermaier1)
, Peter Topolovsek1)
, Tetiana Borzda1)
, Cristian Manzoni2)
,
Daniele Brida3)
, Giulio Cerullo2)
, Dragan Mihailovic1)
1)
Department of Complex Matter, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia 2)
Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan,
Italy 3)
Department of Physics, University of Konstanz, PO box M 696, 78457 Konstanz, Germany
E-mail: [email protected]
Bulk MoS2 is an indirect semiconductor with a gap of 1.3 eV, which also shows a direct
bandgap transition at 1.9 eV. Upon thinning to few- and ultimately single layers, the indirect
gap strongly increases, while the direct gap remains almost unaffected, which leads to the
crossover from indirect to direct semiconductor in the single-layer limit. Two excitonic levels
are associated with the direct gap, which give rise to photoluminescence, whose quantum
efficiency decreases rapidly with increasing number of layers. Time-resolved fluorescence
and differential transmission studies suggest a multifaceted relaxation behavior which
involves defect assisted intraband scattering, exciton trapping, strongly temperature
dependent carrier-phonon scattering, and interband transitions. When blended with a low-gap
conjugated polymer, few-layer MoS2 flakes act as efficient electron acceptors, enabling the
use in low-cost bulk heterojunction photovoltaic cells.
57
TuII-1 Broad band anti-Stokes white emission in rare earth systems
W. Strek, L. Marciniak, D. Hreniak
Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw,
Poland
E-mail: [email protected]
The efficient broad band anti-Stokes white emission (BASWE) in RE systems induced by
infrared laser excitation is presented. Such process occurres as a result of multiphoton
absorption in rare earth materials (powders, nanocrystals, ceramics and crystals) placed in
vacuum and is characterized by threshold dependence on excitation power. The power
dependence of BASWE intensity is associated with high order parameter N dependent on
excitation density, vacuum pressure and environment temperature. The temperature of
BASWE is relatively low, less than 8000C. It is concluded that the origin of BASWE is
associated with the Ln2+
-CT emission following the avalanche process because it is
characterized by long rise times and saturation at high power excitation. It was found that
BASWE is accompanied by efficient photocurrent which may be controlled by applied
voltage.
58
TuII-2 Visualizer of UV images on the huntite-like glasses co-doped with Ce, Tb and Sb
G. E. Malashkevich1,2)
, V. N. Sigaev2)
, N. V. Golubev2)
, E. Kh. Mamadzhanova2)
,
M. Z. Ziyatdinova2)
, T. G. Khottchenkova1)
, A. A. Sukhodola1)
1)
B.I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, 220072,
Prospect Nezalezhnastsi, 68, Minsk, Belarus 2)
International Laboratory of Functional Glass-Based Materials, D.I. Mendeleev University of
Chemical Technology, 125047, Miusskaya sq., 9, Moscow, Russia
Recently we have shown that transformation of SmxY1–xAl3(BO3)4 huntite polycrystals to the
transparent glass of the identical composition is accompanied by increase of minimal distance
between the Sm3+
ions from 0.59 to 0.67 nm [1]. The huntite-like glassy host-matrix is
characterized by a relatively short-wavelength position of fundamental band and can contain
an activator impurity up to 4.51021
ions/cm–3
. It refers such glasses to attractive objects for
elaboration of different optical and laser materials. The aim of present work is a development
of similar glasses doped with Ce and Tb for application as UV images visualizers.
However, it was turned out that addition of Ce and Tb leads to formation of significant share
of non-luminescing Ce(IV) and Tb(IV) oxygen complexes in glasses melted under air
atmosphere. As a result such glasses were characterized by a weak luminescence. For
prevention of the complexes formation, we used stibium whose triply charged ions possess by
appreciable luminescence in the glass (see Fig. 1, curve 1). At doping of Ce- and (or) Tb-
containing glasses with Sb, these rare-earth elements are stabilized in the triply charged form
displaying an intense luminescence (curve 2 and 3). It was established that concentration
quenching of Tb3+
ions in such glasses is practically absent and in spite of the large minimal
distance between the co-activators an effective transfer of excitations from Ce3+
and lesser
effective one from Sb3+
to Tb3+
take place. At the same time, the Sb3+
ions are quenchers of
Ce3+
ions luminescence. Judging from the stated we determined a range of these co-activators
optimal concentration which provides a full absorption of UV-radiation at 320 nm in layer
thickness 100 m (in compliance with curve 4). Luminescence quantum yield changes
from close on 100% to 20% at scanning of exc on the excitation band (curve 5). It is noted a
relatively high optical resistance of the glasses to the powerful UV radiation.
Fig. 1. Spectra of (1–3) luminescence, (4) absorption and (5) excitation luminescence of (1) Sb-, (2) Ce–
Sb- and (3, 4) Ce–Tb–Sb-containing huntite-like glasses. exc = (1–3) 280 nm, rec = (5) 545 nm.
[1] Malashkevich G.E., Sigaev V.N., Golubev N.V. et al., Materials Chemistry and Physics,
2012, vol. 137, pp. 48–54.
200 400 600
100
200
k (
cm-1
)
(nm)
Inte
nsi
ty (a
. u.)
5
0.0
0.5
1.0
1
2
3
4
59
TuII-3 Advances in Electron Paramagnetic Resonance of Transition Elements
in Materials for Quantum Electronics (YAG, YLuAG, YAP, YLuAP, ZnSe)
H. R Asatryan, D. D. Kramushchenko, P.G. Baranov
A.F. Ioffe Physical-Technical Institute of RAS, Politekhnicheskaya 26, Saint-Petersburg,
194221, Russia
E-mail: [email protected]
The results of electron paramagnetic resonance (EPR) investigations of the laser and
scintillator single crystals are presented, in particular, Y3Al5O12:Ce3+
, (Y1-xLux)3Al5O12:Er3+
,
YAlO3:(Er3+
, Ce3+
Nd3+
), Y(1-x)LuxAlO3:Се3+
, PbGa2S4:(Dy3+
, Nd3+
, Се3+
) and ZnSe doped by
Cr, Co, Fe and Er.
Single crystals of Y3Al5O12 (YAG) and YAlO3 (YAP) activated by rare-earth ions are
widely used in quantum electronics. The interest aroused in these compounds in recent years
stems from the possibility of using Ce-activated YAG and YAP as effective fast-response
scintillators for positron-emitting tomography (PET-imaging) in medicine.
EPR signals of Er3+
, Се3+
and Nd3+
ions in YAlO3 are detected and analyzed. The
main values of g tensors and hyperfine interaction constants for Er3+
and Nd3+
odd isotopes
are determined. The orientation of the local magnetic axes of paramagnetic centers relative to
the YAlO3 crystallographic directions are shown to depend on the actual rare-earth species.
The Ce3+
ion EPR spectrum in Y3Al5O12 and YAlO3 exhibits a number of weaker lines which
crowd around the main cerium lines. These lines are apparently due to such Ce3+
ions whose
nearest environment contains a defect distorting the crystal field. These defects are very likely
to be the Y3+
ions substituting for the Al3+
ions in the octahedral sites.
In compositionally disordered compounds YLuAG and YLuAP several new
paramagnetic Er3+
and Ce3+
centers are observed in comparison with YAG and YAP. These
centers appear as a result of the changes in the crystal field symmetry and magnitude due to
the isomorphic substitution of Lu3+
for Y3+
. The origin of these new centers is established and
their formation probability is calculated depending on the content of the additional lutetium
impurity. The additional lines of Ce3+
in YLuAP have different intensities; however,
qualitatively they are similar to the satellite lines observed in YAlO3.
In the mid infrared (IR) range, the wavelength region 2–5 μm is of great interest,
because the radiation in this region corresponds to the so-called “transparent window” in the
Earth’s atmosphere, which leads to a small loss of the light during its propagation in the
atmosphere. The PbGa2S4 and ZnSe crystals are corresponding to these requirements.
EPR signals of Dy3+
, Nd3+
and Ce3+
in lead thiogallate (PbGa2S4) single crystals are
detected and analyzed for the first time. Possible mechanism of the charge compensation for
heterovalent substitution of Pb2+
by RE3+
in lead thiogallate single crystals is analyzed.
The EPR spectra observed in zinc selenide (ZnSe) crystals doped with transition
elements have been analyzed and identified. It has been shown that, in addition to working
impurities (Cr2+
, Co2+
, or Fe2+
), the diffusion layer exhibits EPR spectra of accompanying
impurities due to the diffusion of transition elements used in the preparation of active
materials for quantum electronics operating in the mid-IR range. EPR diagnostics of these
impurities can be used in the development of appropriate regimes for minimizing
concentrations of accompanying impurities that adversely affect the performance
characteristics of laser materials. It has been found that, during the diffusion of transition
metals, ions of the trace impurity Mn2+
, which is characterized by extremely informative EPR
spectra, are embedded in the crystal lattice. It has been proposed to use these ions as ideal
markers to control, on the electronic level, the crystal structure of the active diffusion layer.
60
TuII-4 Spectroscopic properties of new cubic tungstates doped with Eu3+
and Yb3+
ions
M. Guzik
1), K. Bartosiewicz
1), M. Bieza
1), J. Iwańska
1), Y. Guyot
2), E. Zych
1), G. Boulon
2)
1)
Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, PL-50-383 Wroclaw, Poland 2)
Institute Light Matter, UMR5306 CNRS-University of Lyon1, University of Lyon, 69622
Villeurbanne, France
E-mail: [email protected]
The motivation for this research was to find nanoscale tungstates with cubic structure,
which then can be used to obtain the transparent ceramics. To our best knowledge any
transparent ceramics of the rare-earth doped tungstates are not known and described in the
literature, so obtaining them is therefore a great challenge.
Two new classes of cubic compounds doped with Eu3+
and Yb3+
ions i.e. nano-and
microcrystalline tungstates of chemical formula Ba3Y2WO9 (Fig.1) and microcrystalline
BaLaLiWO6 were synthesized by sol-gel method. For Ba3Y2WO9 X-ray diffraction (XRD)
analysis demonstrates single-phase nanopowders with high crystallite dispersion, and
confirmed crystallization in cubic perovskite with the space group Fm-3m. However, for
BaLaLiWO6 only microcrystalline powder, despite the use of the same conditions of
synthesis, confirmed by SEM method was obtained. The luminescence excitation and
emission spectra in the ultraviolet-visible (UV) and NIR region at room and low temperature
were used to investigate the optical properties of these phosphors. The investigations were
completed by the site-selective excitation with luminescence and decay measurements.
The comprehensive spectroscopic results will be presented and discussed in depth.
Fig. 1 SEM micrographs of Ba3Y2WO9: Eu3+ ion and crystal structure of Ba3Y2WO9.
61
TuII-5 Optical properties of crystals doped with Sm3+
or Dy3+
relevant to potential
InGaN/GaN laser diode-pumped visible laser operation: A comparative study
Witold Ryba-Romanowski1)
, Adam Strzęp1)
, Radosław Lisiecki1)
, Marek Berkowski2)
1)
Institute of Low Temperature and Structure Research, Polish Academy of Sciences,
Wrocław, Poland 2)
Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
Accomplishment of practically useful visible laser operation in crystalline media is a
tempting issue. However, up to now the ruby laser discovered over 50 years ago still remains
the only practical laser device emitting visible radiation. The main reason for the lack of
progress in this field is related to the fact that potential upper laser levels would be inevitably
located at high energy thereby limiting the spectral range accessible for optical pumping to a
narrow energy region between the upper laser level and the UV absorption edge of a laser
medium. As a consequence early attempts to achieve a flashlamp-pumped visible laser
operation in crystals doped with Pr3+
, Eu3+
, Dy3+
, Ho3+
and Er3+
, albeit successful, revealed a
poor absorption efficiency, hence a marginal laser performance. Accordingly, currently
available sources of coherent light in the visible region consist of frequency doubled infrared
lasers, or optical parametric oscillators (OPO) operating in a pulsed regime.
Spectacular recent progress in the development of blue-emitting semiconductor laser
diodes opens a new approach to the problem of optical pumping efficiency and makes a
design of all-solid-state visible lasers much closer. In fact, available output powers of blue
laser diodes become high enough to achieve threshold for laser operation and their emission
wavelength can be advantageously matched to absorption bands of rare earth-doped crystals.
Among rare earth ions trivalent samarium and dysprosium ions deserve some special
attention because their emission occurs predominantly in the visible with the most intense
emission lines consistent with a potential four-level laser system. In this study our results of
detailed spectroscopic investigation of Sm3+
and Dy3+
ions incorporated in crystal structures
of YAl3(BO3)4, LiNbO3, Gd3Ga5O12, Gd2SiO5, Lu2SiO5 and (Gd,Lu)2SiO5 are reported and
analysed. Particular attention was paid to the impact of the hosts on transition intensities and
linewidths of incorporated luminescent ions. The nature and pertinence of line broadening has
been assessed based on low temperature absorption and emission spectra. Contribution of non
radiative energy transfer processes to the relaxation of the 4G5/2 level of Sm
3+ and the
4F9/2
level of Dy3+
was determined from luminescence decay curves. Fundamental spectroscopic
parameters relevant to potential laser operation in systems under study were evaluated and
discussed. It follows from these considerations that samarium-doped crystals show promise
for future application owing to the combination of a strong absorption that matches emission
wavelength of commercial laser diodes emitting near 405 nm, long luminescence lifetime
with a small contribution of multiphonon decay and favourable branching ratios for visible
luminescence. Major shortcoming of dysprosium-doped crystals results from a weak intensity
of absorption bands available for optical pumping near 450 nm and 385 nm combined with
relatively strong self-quenching of luminescence.
Acknowledgements
This work is supported by the NCN under grant DEC – 2011/01/B/ST7/06166
62
TuII-6 Nonresonant excitation of Er3+
ions in matrices containing Si nanocrystals
I. N. Yassievich
A.F. Ioffe Physical-Technical Institute of RAS, Politekhnicheskaya 26, Saint-Petersburg,
194221, Russia
Rare-earth (RE) ions are favorite “optical dopants” frequently used to tailor optical properties
of insulating and semiconducting hosts. Among insulating hosts, the SiO2 matrix doped with
Er3+
ions (SiO2:Er) is well investigated as the basis for the development of optical amplifiers.
However, due to the fact that the optical properties of RE ions are determined by the inner 4f
electron shell, the SiO2:Er-based amplifiers require high-power resonant pumping, which is
cumbersome and expensive. Excitation of photo- and electro-luminescence of Er3+
ions in
SiO2 can be effectively sensitized by Si quantum dots (SiQDs). In this case, room-temperature
1.54-μm Er-related emission can be induced by a nonresonant excitation process via band-to-
band absorption in SiQDs. Since the indirect band structure of Si is preserved also in its
nanocrystalline form, electron-hole pairs generated in this way are characterized by a
relatively long lifetime, enabling energy transfer to Er3+
ions located in the vicinity. Making
use of the band-to-band absorption, this indirect excitation process is relative efficient, with
an (effective) excitation cross section of σ ≈ 10−17
–10−16
cm2. As a result, an increase of a
factor about 100 in σ is found in comparison with SiO2:Er.
We discuss the experiments which have revealed that the excitation of Er3+
ions in the
SiO2:(Er,SiQDs) system involves mechanisms operating on different timescales, from several
microseconds down to below 100 ns. In particular, the Forster (dipole-dipole) mechanism has
been proposed in order to explain the “slow” (microsecond time scale) energy transfer from
SiQDs, to Er3+
ions, and the microscopic location of Er with respect to SiQDs has been
considered. In addition to this relatively slow excitation, the presence of a much faster (sub-
100-ns range) process has been conclusively established. As for its physical origin, a process
analogous to hot-carrier impact excitation of Er in bulk Si has been put forward. In this
mechanism a hot carrier loses (part of) its excess energy by intraband relaxation with energy
transfer to an Er3+
ion.
We present also evidence of a very specific energy-transfer path, in which two Er3+
ions are
excited simultaneously by a single photon of sufficiently high energy absorbed in a SiQD.
This excitation mechanism is enabled by the proximity of Er dopants and bears a strong
similarity to quantum cutting observed for RE ions. It operates parallel to the Forster dipole-
dipole process and Auger-facilitated energy-transfer mechanisms.
The luminescence of rare-earth ions in isolating matrices is often intensified by defects
associated with RE ions or excitons bound to these defects. The following mechanism of
sensitization is usually assumed: bound excitons (or excited defects) are created as a result of
the optical absorption, then the energy is transferred to RE ions in the process of non-radiative
recombination of excitons due to Coulomb interaction (the Foster dipole–dipole
mechanism).
We consider the possibility of excitation of RE ion luminescence directly in the process of
the optical absorption due to the second order perturbation process (the virtual Auger
process). In this case, the energy of incoming photons is less or larger than the exciton energy
and is transmitted directly to RE ions in the process of optical absorption. If there is an excess
of energy, the excitation process is accompanied by phonon emission. We demonstrate the
efficiency of the virtual Auger process.
63
TuII-7 Spectroscopic and laser properties of Zn1-xMgxSe single crystals doped
with Fe2+
ions at room and low temperatures
M. E. Doroshenko1)
, T.T. Basiev1)
, V. V. Osiko1)
, H. Jelinkova2)
, M. Jelinek2)
,
Y. A. Zagoruiko3)
, N. O. Kovalenko3)
, A. S. Gerasimenko3)
, V. M. Puzikov3)
1) A.M. Prokhorov General Physics Institute RAS, Moscow, Russia.
2) Czech Technical University, Prague, Czech Republic.
3) Institute for Single Crystals NAN, Kharkov, Ukraine.
In the last several years a growing demand for room-temperature tunable mid-infrared sources
is observed. The ZnSe:Fe2+
crystal was demonstrated to be a perspective source for tunable
mid IR lasers. Unfortunately, due to multiphonon quenching the lifetime of Fe2+
ions at room
temperature is quite short (about 300 ns). This problem could be solved by cooling the
ZnSe:Fe2+
crystal to low temperatures but strong shortening of the fluorescence spectrum
especially at long wavelength wing is observed in this case. To overcome this drawback,
Zn1-xMgxSe solid solutions doped with Fe2+
could be applied. In this work we report the
spectroscopic and laser properties of Fe2+
doped Zn1-xMgxSe crystals (x=0.2, 0.4) at room and
low temperatures.
Fe2+
doped ZnMgSe crystal with ~20% and ~40% of Zn ions substituted by Mg ions were
synthesized using Bridgeman technique. Fe2+
ions doping was performed during the synthesis
process. The absorption and fluorescence spectra corresponding to the 5E→
5T2 vibronic
transition in the Fe2+
ions were measured and recalculated using Fuchtbauer-Ladenburg
equation and reciprocity method to cross section spectra as shown in Fig.1 for Zn0.8Mg0.2Se
crystal. The maximum value of emission cross-section of Fe2+
ions in Zn0.8Mg0.2Se crystal
was found to be about 1.7x10-18
cm2 which is slightly lower that in ZnSe crystal (2x10
-18
cm2). The absorption and fluorescence spectra of Fe
2+ ions in Zn0.8Mg0.2Se crystal were
shown to be shifted 300 nm towards longer wavelengths if compared to that in ZnSe:Fe2+
crystal. The increase of Mg concentration up to ~40% was shown to cause additional ~200
nm shift of Fe2+
fluorescence maximum towards longer wavelengths.
Wvl, ZnSe vs Fluor_calc
Wavelength, nm
2000 3000 4000 5000 6000
Cro
ss-s
ecti
on
, cm
2
0.0
5.0e-19
1.0e-18
1.5e-18
2.0e-18
Zn0.8
Mg0.2
Se:Fe2+
Room Temperature
Absorption
Emission
Meas.
Calc.
Col 7 vs Col 8
Time, s
0 10 20 30 40
I/Io
0.01
0.1
1
1=2 s
2=10 s
Zn0.8
Mg0.2
Se:Fe2+
90 K
Fig.1 Calculated absorption and emission cross-section Fig.2 Measured decay curve of Fe2+ ions in
of Fe2+ ions in Zn0.8Mg0.2Se crystal. Zn0.8Mg0.2Se crystal at 90K.
The fluorescence spectrum of Zn0.8Mg0.2Se:Fe2+
crystal at low (~90K) temperature was
narrowed compared to room temperature one but not so drastically as in case of ZnSe crystal.
The decay curves measured in wide temperature range were shown to be double exponential.
The Fe2+
ions lifetime measured at room temperature was estimated to be about 120 ns but
was fast grown with temperature decrease up to 10 ms at 90 K (see Fig.2). Laser properties of
Zn1-xMgxSe:Fe2+
crystals under short and long pulse 2.94 m optical pumping at low
temperatures were investigated and 4800 nm lasing at 90 K was demonstrated.
64
TuII-8 Influence of excited configurations on intensity of electric dipole transitions
of rare-earth ions
E. B. Dunina, A. A. Kornienko
Vitebsk State Technological University, 210035, Vitebsk, Belarus
E-mail: [email protected]
The classical Judd-Ofelt theory of electric dipole transitions [1,2] is widely used for
description of absorption and luminescent transitions of rare-earth ions in glasses and crystals
already more than 50 years. For this time the examples of inadequacy of the Judd-Ofelt theory
to some ions and systems were found out. Some attempts to improve the Judd-Ofelt theory
(see example [3-6]) did not affect the main problem – the correct account for influence of an
environment on multiplets of rare-earth ions.
In this talk the results of the detailed investigation of excited configurations influence
on intensities of intermultiplet transitions are reported.
Any theory is grounded on one or several approximations. In the Judd-Ofelt theory,
the influence of excited configurations is taken into account roughly. Approximations used in
this theory can be termed as weak configuration interaction. Depending on a degree of
influence of excited configurations it is possible to distinguish intermediate configuration
interaction as in the modified theory [7] or strong configuration interaction as in [8].
However, in these theories it is not taken into consideration that various excited
configurations have much different energies. This is taken into account in the approximation
which it is possible to name as abnormally strong configuration interaction [9].
Examples of application of various models for the description of intensities of
absorption and luminescent transitions are considered.
[1] B.R. Judd, Phys. Rev. 127 (1962) 750-761.
[2] G.S. Ofelt, J. Chem. Phys. 37 (1962) 511-520.
[3] K. Jankowski et al, Molec. Phys. 38 (1979) 1445-1457.
[4] M.C. Downer et al, J. Chem. Phys. 89 (1988) 1787-1797.
[5] P. Goldner et al, J. Appl. Phys. 79 (1996) 7972-7977.
[6] L. Smentek, J. Alloys & Comp. 380 (2004) 89-95.
[7] A.A. Kornienko et al, Phys. Stat. Sol.(b). 157 (1990) 267-273.
[8] A.A. Kornienko et al, Optics and Spectroscopy 81 (1996) 871-874.
[9] E.B. Dunina et al, Cent. Eur. J. Phys. 6 (2008) 407-414.
65
TuII-9 Processes of energy migration and transfer in Gd-rich
rare-earth doped phosphates
A. Krasnikov1)
, T. Shalapska1)
, G. Stryganyuk2)
, A. Voloshinovskii3)
, S. Zazubovich1)
1)Institute of Physics, University of Tartu, 51014 Riia 142, Tartu, Estonia
2)Helmholtz Centre for Environment Research, 04318 Permoserstr. 15, Leipzig, Germany
3)Ivan Franko National University of Lviv, 79005 Kyryla i Mefodiya 8, Lviv, Ukraine
Ce3+
-doped phosphates can be prospective materials for scintillator applications due to their
high light yield, short decay time, high stability, and low cost. The phosphates doped with
some other rare-earth ions (e.g., Eu3+
) can be used in LED and as display phosphors. The
material performance depends on the efficiency of the excitation energy transfer from the host
lattice to an impurity ion. In the Gd-rich phosphates, due to a strong overlap of the absorption
and emission bands of Gd3+
, an effective energy migration through the Gd3+
sub-lattice and
the subsequent energy transfer from a Gd3+
ion towards an adjacent impurity ion is possible.
Our aim was to study the luminescence characteristics of Ce3+
- or Eu3+
-doped phosphates
of the type of MGdP4O12 (M: Li+, Na
+, Cs
+) and GdP3O9 and to clarify the processes of energy
migration along Gd3+
ions and energy transfer between the Gd3+
and Ce3+
or Eu3+
ions in the
phosphates of different structures and with different alkali metal ions. For that, the steady-
state and time-resolved emission and excitation spectra and luminescence decay kinetics were
measured in the 4.2-300 K temperature range for the Ce3+
- and Eu3+
-doped LiGdP4O12,
NaGdP4O12, CsGdP4O12 polyphosphates [1,2] and the Ce3+
-doped GdP3O9 metaphosphate [3].
In the phosphates studied, the thermally stimulated high-energy shift of the Gd3+
emission
band, observed in the 4.2-150 K temperature range, is caused by the thermal population of the
higher-energy 6P5/2 level of the relaxed
6PJ excited state of Gd
3+. This improves the resonance
conditions among the Gd3+
levels and, thus, leads to the increase in the excitation energy
migration efficiency along the Gd3+
sub-lattice. Much stronger changes in the emission
intensity and decay time observed at T>150 K are due to the thermally stimulated population
of the highest 6P3/2 level of the
6PJ
excited state of Gd
3+. This enhances a spectral overlap of
the Gd3+
and Ce3+
(Eu3+
) bands and results in the increasing probability of the Gd3+
Ce3+
(Eu3+
) nonradiative energy transfer, which appears in the increasing yield of the Ce3+
(Eu3+
)
emission, reduction of the Gd3+
emission and shortening of its decay time. The activation
energies obtained for the above-mentioned 6P7/2
6P5/2 and
6P7/2,
6P5/2
6P3/2 phonon-
assisted processes are in agreement with the energy distances between the corresponding 6PJ
levels. The reverse Ce3+
Gd3+
energy transfer takes place at 4.2-300 K. At 300 K, the
bidirectional Gd3+
Ce3+
energy transfer leads to the equilibrium between the Gd3+
and Ce3+
excited states. Due to a long (s-ms) decay time of the Gd3+
emission, these processes result
in the appearance of undesirable slow components in the decay kinetics of the Ce3+
emission.
In the Ce3+
-doped Pr3+
-rich phosphates of the type of MPrP4O12 and PrP3O9, the energy
migration along the Pr3+
sub-lattice and the Pr3+
Ce3+
energy transfer are also possible [4].
Unlike the Gd3+
emission, the decay kinetics of the Pr3+
emission is fast (ns). Owing to that,
the Pr3+
Ce3+
energy transfer does not result in the appearance of slow decay components
that makes the Pr3+
-rich compounds suitable for fast scintillator applications.
[1] G. Stryganyk, et al., J. Lumin. 131, 2027 (2011).
[2] P. Demchenko, et al., J. Phys. D: Applied Physics (2013).
[3] A. Krasnikov, et al., Phys. Status Solidi B, 1-8 (2013) / DOI 10.1002/pssb201349020
[4] T. Shalapska, et al., J. Phys.: Condens. Matter 25, 105403 (2013).
66
TuII-10 Selective excitation of energy transfer processes from host excitations
to doped ion in Li(Lu,Y)F4:Ce crystals
A. Belsky
Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon 69622
Villeurbanne cedex, France
E-mail: [email protected]
VUV time-resolved study and simulation of energy transfer chain (reabsorption, ionization
and capture, dipole-dipole transfer) to Ce3+
doped ion from different type of host excitations
of Li(Lu,Y)F4 crystal matrix will be discussed.
The parameters of these transfer processes can be evaluated from the analysis of decay and
raising kinetics of luminescence excited by short pulses of irradiation. The selective excitation
of different initial states is useful for separation of various transfer processes. These initial
stages of transfer chains can be excited by photons with varying energies from UV to soft X-
rays.
Synchrotron radiation sources provide the unique possibility to excite selected initial states
with high energy resolution. The excellent time stability and picosecond pulse duration allows
one to measure both fast raising stages and obtain even small deviations from exponential
decay law. Therefore SR experimental setups for spectral-kinetic measurements are important
in obtaining quantitative data.
The decay kinetics for different excitation photon energies can be treated only if we
understand the models of relaxation processes typical for each initial state. When the
luminescence decay is measured for wide range of excitation photon energies from the
activator absorption band up to energies several times higher than the forbidden gap energy,
the sets of relaxation processes becomes more and more complicated. In this case some
parameters obtained for decays for low-energy excitation can be used for simulation of decays
at high-energy excitation.
The simulation approach presented in this report takes into account the superposition of decay
responses from the train of pulses of synchrotron radiation, effects of reabsorption of the
luminescence light, dipole- dipole and diffusion-controlled energy transfer between activators
and excitons, and surface losses. The sequential analysis of spectral series of decay curves
significantly increases the reliability of simulation results and reduces the number of varying
parameters.
67
TuII-11 Research on rare earth-doped sesquioxide ceramics elaborated by
Spark Plasma Sintering (SPS) method
G. Alombert-Goget1)
, Y. Guyot1)
, G. Boulon1)
, M. Guzik2)
,
A. Ito3)
, T. Goto3)
, M. Koichi3)
, A. Yoshikawa3)
1)
Institute Light Matter, UMR5306 CNRS-University Lyon1, 69622 Villeurbanne, France 2)Faculty of Chemistry, University of Wroclaw, PL-50-383, Wroclaw, Poland
3)Institute for Materials Research, Tohoku University, 980-8577, Sendai, Japan
Research on transparent sintered polycrystalline ceramics is under progress with the synthesis
of new laser ceramics at the frontier of materials science, with high melting points like
sesquioxydes. Among un-doped sesquioxide materials which are optically un-active (Sc2O3,
Y2O3, Lu2O3), the Lu2O3 crystalline compound is of special interest due to the highest thermal
conductivity (12.5 W/m/K) and the lowest phonon energy (391cm-1
) comparing with YAG
(700cm-1), have been suggested to be potential materials for high power lasers. However it is
extremely difficult to grow Lu2O3 single crystal using conventional crystal growth methods
because of its high melting point (2490 °C). Indeed, it is much easier to fabricate Lu2O3 into a
ceramic structure -solid-state reaction process- because the sintering temperature is about
700 °C lower than its melting point and no expensive crucible is required.
Our first program involves Nd3+
/Yb3+
-doped Lu2O3 and we will report here only Nd3+
-doped
Lu2O3. Until now, there are few reports on laser properties of Nd3+
-doped Lu2O3 single
crystals. A recent one in 2011 [1] points out a specific multiple wavelengths lasing at 1076
and 1080 nm Dual-wavelength laser has potential applications for new-wavelength laser by
sum-frequency, coherent terahertz (THz) generation by difference frequency and ultrahigh
repetition rate pulse by optical beating.
In this work, we will show the process used to get for the first time Nd3+
-doped Lu2O3
transparent ceramics by the spark plasma sintering (SPS) method, a non-conventional one [2]
and we will characterize carefully both, structural properties by TEM, thermal conductivities
and spectroscopic data by looking more especially on Nd3+
ions distribution. Absorption
spectra will be analyzed mainly around the 4I9/2
4F5/2;
2H9/2 absorption transitions of the laser
diode pumping and the
4I9/2
4F3/2 absorption transitions of the emitting level. Emission
spectra of the expected laser lines 4F3/2
4I11/2, at both 1076.4 nm (R1Y1) and 1080.5 nm
(R1Y2) and concentration dependence of the 4F3/2 decays will also been detailed. In
addition, we will give some data on the distribution of Nd3+
ions from the resolved absorption
spectroscopy recorded at 4K, mainly on the inhomogeneous distribution of C2-C2 and C2- C3i
pairs respectively and an essay will be done to interpret site selective spectroscopy from the
occupation of the two Nd3+
C2 and C3i sites [3].
[1] Liangzhen Hao and al. Optics Express 19, No. 18 (2011) 17774-17779
[2] L. An, A. Ito, T. Goto, J. Amer. Ceramics Soc. 94 (2011) 695-698
[3] G. Alombert-Goget, Y. Guyot, G. Boulon, M. Guzik, A. Ito, T. Goto, M. Koichi, A.
Yoshikawa, to be published.
68
TuII-12 Magnetooptical time-resolved study of Eu2+
spins dynamics in
EuFe2(As1-xPx)2 pnictide superconductor
A. Pogrebna,1)
Z. A. Xu,3)
T. Mertelj,1)
D. Mihailovic1,2)
1) Complex Matter Department, Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana,
Slovenia 2)
Center of Excellence on Nanoscience and Nanotechnology – Nanocenter (CENN
Nanocenter), Jamova 39, SI-1000 Ljubljana, Slovenia 3)
Department of Physics, Zhejiang University, Hangzhou 310027, People’s Republic of China
E-mail: [email protected]
Employing optical pump-probe femtosecond spectroscopy we investigate the Eu
2+
dynamics in EuFe2(As0.7P0.3)2 (EFAP) pnictide superconductor and parent
nonsuperconducting EuFe2As2 (EFA) in magnetic field. In both cases we observe an
emergence of a slow anisotropic photoinduced relaxation component concurrent with Eu spin
ordering. A remarkable change of the quasiparticle relaxation dynamics at the
antiferromagnetic (AFM) spin density wave (SDW) transition temperature 200 K is observed.
The evolution of the photoinduced reflectivity transients with magnetic field in the
superconducting EFAP is different than in the nonsuperconducting EFA. In EFA we observe
switching of the optical-transients anisotropy with increasing magnetic field attributed to a
field-induced antiferromagnetic (AFM) to ferromagnetic (FM) phase transition. In the
superconducting EFAP a large coherent magnon oscillation is observed at a similar
metamagnetic transition. The oscillation is absent in the transient magneto-optical Kerr effect
suggesting an interplay between the Eu2+
spin and charge degrees of freedom.
[1] Zhi Ren et al. Phys. Rev. B 78. 052501 (2008)
[2] S.Zapf et al. Phys.Rev. B 84, 140503(R) (2011)
[3] Z. Guguchia et al. Phys. Rev. B 84, 144506 (2011)
69
TuII-13 Pump-induced processes in Ce3+
:CaF2 crystals co-doped by Yb3+
and Lu3+
ions
S. A. Shnaidman, A. S. Nizamutdinov, V. V. Semashko, M. A. Marisov
Kazan Federal University, 420008, Kremljovskaja str., 18, Kazan, Russia
The CaF2:Ce3+
crystals show advantageous spectral characteristics for broad UV
amplifying medium application but have poor photochemical stability due to wide variety of
photodynamic processes [1,2]. Here we are encouraged in managing these processes and
therefore optical properties with crystal-chemical approach which could result in design of
new solid state devices for photonics applications [3]. This work was aimed at dynamic
processes investigation induced by laser radiation of UV spectral range by pump-probe
studies in CaF2-LuF3 crystals doped with Ce3+
and Yb3+
ions and has carried out
comprehensive research into new materials for quantum electronics – fluoride crystals with
fluorite-type crystal structure CaF2-LuF3 solid solutions doped with Ce3+
and Yb3+
ions.
Experiments on optical spectroscopy reveal the formation of new types of impurity
centers and excitation trapping for Ce3+
interconfigurational transitions in CaF2-LuF3:Ce3+
and CaF2-LuF3:Ce3+
+Yb3+
with high concentration of dopants (0,2-2 at. %). Investigation of
long living induced absorption lines and spectral dependence of small signal gain coefficient
in these crystals have shown complex picture of photochromic centers which could be used to
form saturable absorbers, periodic structures and optically driven switches for UV and VIS
spectral range [4]. The pump-probe technique allowed us to observe nonlinear dynamic in
absorption coefficient vs pumping radiation intensity occurring due to excited state absorption
and free charge carriers distribution among impurity centers. Computer simulation based
interpretation allowed us to reveal role of cationic set in managing optical characteristics and
spatial properties of photochromic centers. As result optical gain was observed on
CaF2:Ce3+
+Yb3+
in the range 325-335 nm for the first time which justifies the proposed
mechanism for crystal chemical managing. Also optimal chemical content was proposed for
fluoride crystals with fluorite-type crystal structure CaF2-LuF3 solid solutions doped with
rare-earth ions for applications as UV active medium and optically driven switch. This work
was supported by RFBR Foundation grant.
[1] D. J. Pogashnik, D. S. Hamilton. Phys. Rev.B. 36 (1987) 16, 8251.
[2] R. Yu. Abdulsabirov, S. L. Korableva, A. S. Nizamutdinov, M. A. Marisov, A. K. Naumov,
V. V. Semashko. Proc. SPIE 6054 (2006) 172.
[3] A.S. Shcheulin, A.K. Kupchikov, A.I. Ryskin. Optics and Spectroscopy 107 (2009) 1, 164.
[4] Y. Tanaka, J. Upham, T. Nagashima, T. Sugiya, T. Asano, S. Noda. Nature materials 6
(2007) 862
70
TuII-14 Photoconductivity and photodielectric effect in LiY1-xLuxF4 crystals
doped by Ce3+
and Yb3+
ions
V. V. Pavlov, V. V. Semashko, R. M. Rakhmatullin, S. L. Korableva, L. A. Nurtdinova
Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russian Federation
Photodynamic processes (PDP) induced by UV laser pumping of the activated solid-state
materials are the main obstacle that prevent or impair laser action on 5d-4f
interconfigurational transitions of the rare-earth ions [1]. These processes significantly change
optical and electro-physical properties of the doped crystals because of one- or multi-photon
impurity ionization, free charge carriers (electrons and holes) production in the appropriate
energy bands of the crystal and subsequent their capture by the lattice defects (color center
formation). Therefore key to PDP are the parameters of active ions photoionization spectra
[2]. Besides the knowledge about photoionization spectra feature and photoionization
threshold depended on chemical composition enables to determine the positions of the energy
states of the impurity centers relative to the host bands. It will allow to design the active
materials and to choose the pumping condition for the UV solid-state active media to avoid
degradation of laser properties and to increase laser efficiency.
Here photoconductivity and photodielectric effect spectra in LiY1-xLuxF4 (x=0, 0.5 and 1)
crystals doped by Ce3+
and co-doped by Yb3+
ions are presented and discussed. Time-resolved
responses of the dielectric permittivity of Ce3+
, Yb3+
:LiY1-xLuxF4 crystals versus excitation
radiation wavelength and intensity were studied by the microwave resonant technique [3]. For
the analysis of experimental data the model of photodynamic processes was elaborated. This
model has been used as a basis to calculate the main parameters of photodynamic processes.
The chemical composition impact on photo-physical properties of the samples is analyzed.
Essential role of Yb3+
ions are elucidated because of one of ways to decrease the harmful
influence of photodynamic processes and to improve laser efficiency in Ce3+
doped fluoride
crystals is the co-activation of Yb3+
ions [4]. The optimal chemical composition of Ce3+
ions
doped LiY1-xLuxF4 crystals and pumping conditions are discussed.
Obtained results demonstrate that studies of photoconductivity spectra are extremely
important for the successful design of the effective luminophores, the scintillators and the
UV/VUV active medium.
[1] V.V. Semashko, Phys. Solid State 47, 1507 (2005).
[2] G..J. Pogatshnik and D.S. Hamilton, Phys. Rev. B 36, 8251 (1987).
[3] M.-F. Joubert , S.A. Kazanskii, Y. Guyot, J.-C. Gacon, J.-Y. Rivoire, C. Pedrini, Opt.
Mater. 24, 137 (2003).
[4] A.S. Nizamutdinov, V.V. Semashko, A.K. Naumov, S.L. Korableva, R.Yu. Abdulsabirov,
A.N. Polivin, M.A. Marisov, J. Lumin. 127, 71 (2007).
71
TuII-15 Cathodoluminescent study of energy trap states in ceramics based on YAG:Nd
K. N. Guliaeva, A. N. Trofimov, M. V. Zamoryanskaya
Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Saint Petersburg,
Russia
E-mail: [email protected]
Yttrium-aluminum garnet doped with neodymium (YAG:Nd) single crystal has a lot of
applications in modern science and technology. This material is widely used as a laser
medium. YAG:Nd nanoceramics is conjectured as a prospective laser material. Studying its
luminescent properties has become one of the most significant problems of laser optics.
Ceramics, prepared in a low cost way compared to processing the monocrystal, has
comparable optical and thermomechanical properties and can substitute YAG:Nd single
crystal in many applications. The aim of the work was to study and compare luminescent
properties of YAG:Nd single crystal and YAG:Nd nanoceramics in the infrared, visible and
ultraviolet ranges. Comparing luminescent properties of those materials in a wide optical
range allows to understand the fundamental difference between materials and to consider the
possibility of substitution YAG:Nd single crystal to nanoceramics in many applications.
The CL measurements were performed using X-ray microanalyzer Camebax Microbeam with
optical spectrometer. The method of local CL was used as the main method of research. Due
to the fact that the energy of the electron beam (1 – 35keV) is much greater than the band gap
in YAG, it becomes possible to investigate all optical transitions. When excited by electron
beam, YAG:Nd has a rich intensive luminescence not only in the infrared range, but also in
visible and ultraviolet ranges.
The main results that were obtained:
1. The CL spectra of both materials in all measured ranges are identical;
2. The CL intensity of bands in YAG:Nd single crystal is much higher than the CL
intensity in YAG:Nd nanoceramics;
3. When continuously irradiated by electron beam, the luminescence of YAG:Nd single
crystal decays, but the luminescence of YAG:Nd ceramics rises.
The rise of nanoceramics CL intensity is considered to be caused by energy trap states that
may appear with decreasing of the grain size and presence of the grain boundaries in
ceramics. This effect was not studied earlier. That is the fundamental difference that makes
YAG:Nd nanoceramics prospective for using as a laser medium.
The investigations of the CL intensity increase dependence on temperature and the electron
beam current were made for calculation of the trap state activation energy.
72
TuII-16 LiY0.3Lu0.7F4: Ce3+
, Pr3+
mixed crystal as a perspective upconversionally
pumped UV active medium
V. G. Gorieva, V. V. Semashko, S. L. Korableva, M. A. Marisov
Kazan Federal University, 420008, 18 Kremlevskaya st, Kazan, Russia
Currently tunable solid-state optical quantum generators of UV range are most easily
implemented on interconfigurational 4fn-1
5d - 4fn transitions of rare-earth ions in wide-
bandgap insulators. In this case the pumping of the laser is usually carried out by UV
harmonics of visible and infrared radiation generated by of commercially available lasers, or
powerful radiation of excimer lasers. However, UV pumping radiation induces in solid-state
active elements various photodynamic processes (PDP), which cause degradation of the
optical properties of active media. One of the ways to avoid or significantly reduce harmful
manifestations of PDP is to use up-conversion pumping [1]. Finding ways to realize such
upconversion pumping is particularly important in the view of future implementation of
effective solid-state UV-active media with the use of semiconductor lasers as a pumping
source and compact solid-state quantum electronics devices of UV range in general.
Here we investigate the possibility of effective population of states of 5d-configuration of
Ce3+
ions in LiY0.3Lu0.7F4 (LYLF) crystals by stepwise 3H4-3Pj-4f5d up-conversion excitation
of states of 4f5d-configuration of Pr3+
ions, followed by the transfer of excitation energy from
Pr3+
to Ce3+
ions. We discuss the possibility of increasing energy transfer efficiency in
Pr,Ce:LYLF mixed crystals by doping rising, because before it was the one of obstacles
which prevent optical gain on 5d-4f transitions of Ce3+
ions in Pr,Ce:LiLuF4 crystals [2]. In
particularly, it is shown that the real concentrations of Pr3+
and Ce3+
ions 0.23 at.% and 0.47
at.% are achieved in mixed LYLF crystal respectively. The spectral and kinetic characteristics
of Pr,Ce:LYLF crystal are presented. Absorption cross-sections from the excited 3Pj state to
the 4f5d-states of the Pr3+
ions are estimated and the coefficients of excitation energy transfer
from the Pr3+
ions to Ce3+
ions are determined. It reaches 31% in case of real concentrations of
Ce3+
ions C(Ce) = 0.28% and Pr3+
ions C(Pr) = 0.3% in Pr,Ce:LYLF crystal.
Preliminary results of pump-probe experiments are presented and discussed. Three crystals
with real concentrations of Pr3+
and Ce3+
ions 0,24 at.% and 0,16 at.% ; 0,3 at.% and 0,28
at.% ; 0,23 at.% and 0,47 at.% respectively were studied. Samples were pumped by two π-
polarized laser beams at 595 nm and 266 nm and probing at 325 nm for σ-polarization or
310 nm for π-polarization. The temporary delay between 595 nm and 266 pulses and 266 nm
and probe pulses were about 7 ns and 6 ns respectively.
Obtained results demonstrate good prospects of using crystal LiY0.3Lu0.7F4:Ce3+
, Pr3+
as an
active medium of solid-state laser with up-conversion pumping provided that color center
formation processes suppression and rising Pr3+
-Ce3+
energy transfer efficiency.
[1] V.V.Semashko, M.F. Joubert, E. Descroix, S. Nicolas, R. Yu. Abdulsabirov,
A.K.Naumov, S.L.Korableva, A.C.Cefalas, Proc. of SPIE. (2000), V. 4061, 306-316.
[2] S. Nicolas, E. Descroix, M.F. Joubert, Y. Guyot, M. Laroche, R. Moncorge, R.Y.
Abdulsabirov, A.K. Naumov, V.V. Semashko, A.M. Tkachuk, M. Malinowski, Opt.Mat.
(2003), V.22, 139-146.
73
TuII-17 Ultrashort pulse UV lasers based on Ce3+
activated LiCaAlF6 and LiSrAlF6
crystals
O. R. Akhtyamov, A. S. Nizamutdinov, V. V. Semashko, M. A. Marisov
Kazan Federal University, 420008, Kremlevskaja 18, Kazan, Russia
Modern laser spectroscopy studies require UV laser sources with ultrashort pulse duration.
Here we report on UV laser oscillation on colquiriite structure fluoride mixture crystals of
Ce3+
:LiCaAlF6 (Ce:LiCAF) and Ce3+
:LiSrAlF6 (Ce:LiSAF) active media which can be
operate in 280-315 nm spectral range and provide sub-nanosecond pulse UV lasing.
Fig. 1 Temporal distribution mode-locking Ce:LiCAF
laser (with external mirror).
Fig. 2 Temporal distribution single pulse Ce:LISAF
laser oscillation.
The laser cavity consists of a pulse-seeding laser cavity and a feedback laser cavity as the first
step of experimental approach. The pulse-seeding laser cavity provide spiking mode. Mode-
locking was organized using long feedback cavity [1,2], and as a result a stable ultrashort
“pulse-train” with pulse duration at about 800 ps and a period of 1.59 ns defined by the design
of the cavity (fig.1) are observed. It is important that length of the external cavity should be
tuned so that the second pulse of pulse-train occur before generation of the second stochastic
pike. In this case the lasing pulse is circulating into external laser cavity will use the inversion
and mode-locking will occur preventing stochastic laser oscillation.
The second step was in single picosecond pulse generation experiments. Here we discuss
approach which employs photodynamic processes such as transient absorption due to excited
state absorption and color centers for intracavity losses modulation. We report on single pulse
generation of about 400 ps duration from Ce:LiSAF (fig. 2) in convenient Fabri-Perrot cavity
and discuss conditions of pulse shortening in UV active medium by photodynamic processes.
This work was supported by RFBR Foundation grant and Russian Federation Ministry of
Science grant.
[1] N. Sarukura, Z. Liu, Y. Segawa, V. V. Semashko, and A. K. Naumov et al. J. Appl. Phys.
Lett. (1995) 67, 602.
[2] N. Sarukura, Z. Liu, S. Izumida, M.A. Dubinskii, R.Y. Abdulsabirov, S.L. Korableva. J.
Appl. Opt. (1998) 37, 6446.
74
TuII-18 Photodynamic processes and laser performance of Ce:LiYLuF4
Larisa Nurtdinova1)
, Vadim Semashko1,2)
, Stella Korableva1)
1) Kazan Federal University, 420008, 18 Kremlevskaya st., Kazan, Russian Federation
2) LLC “Ultraviolet Solutions”, 420025, 184-65 Prospect Pobedy st., Kazan, Russian
Federation
Solid-state cerium-doped-fluoride lasers that are directly tunable in the 280–340-nm spectral
region exceed the alternatives (OPO, nonlinear frequency conversion systems) in simplicity,
lasting quality and size, not to mention virtually indefinite potential to increase output power.
In the past decade, cerium-doped UV laser action investigations showed impressive
performance characteristics [1]. At the same time, however, intense excited-state absorption
(ESA) followed by color center formation were established as the principal factors
deteriorating laser performance in Ce-doped fluorides [2]. Investigations of pump-probe gain
and lasing efficiency in LiYXLu1-XF4 (LiYLuF4) crystals doped with Ce3+
and Ce3+
+Yb3+
ions
demonstrated high potential of these solid solutions compared to the well-known active media
LiYF4 and LiLuF4 [3].
Figure 1 a – Spectrum of excited-state photoconductivity (pumping 300 nm) in iY0.4Lu0.6F4:Ce(1%) at
the room temperature; b – temperature dependence of lasing in LiY0.5Lu0.5F4:Ce(2%)
We present the results of photodynamic processes investigations in the context of obtaining
laser action on 5d-4f transitions of Ce3+
in LiYLuF4 crystals. Direct single- and two photon
induced photoconductivity measurements revealed a band centered at about 265 nm in Ce-
doped LiYF4, LiLuF4 and LiYLuF4 crystals (see fig. 1a). The origin of this band is attributed
to 5d-6s ESA of Ce3+
ions, however, absorption of color centers contribution is also to be
considered (depending on the matrix). Laser experiments on Ce:LiYLuF4 have been
performed and temperature dependence of lasing efficiency has been investigated (see Fig.
1b).
[1] D.J. Spence, H. Liu, D.W. Coutts, Opt. Commun.(2006) 262, 238.
[2] D. W. Coutts and A. J. S. McGonigle, IEEE J. Quant. El. (2004) 40, 1430.
[3] A.S. Nizamutdinov, V.V. Semashko, A.K. Naumov, S.L. Korableva, R.Yu.
Abdulsabirov, A.N. Polivin, M.A. Marisov, J. Lumin. (2007) 127, 71.
240 250 260 270 280 290
0
5
10
15
20
25
30
35
pea
k p
ho
tocu
rren
t, n
A
wavelength, nm
LiY0.4Lu0.6F4:Ce3+(1%)
-30 -20 -10 0 10 20 301,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
lasi
ng
ou
tpu
t, m
W
temperature, oC
LY0.5Lu0.5F4:Ce3+(2%)
las =310 nm, 10Hz
b
a
75
We-1 Advances of polycrystalline transparent laser ceramics
G. Boulon1)
, M. Guzik2)
, T. Epicier3)
, L. Esposito4)
, T. Goto5)
, A. Yoshikawa5)
, A. Ikesue6)
1)
Institute Light Matter, UMR5306 CNRS-University Lyon1, University of Lyon, 69622
Villeurbanne, France 2)Faculty of Chemistry, University of Wroclaw, PL-50-383, Wroclaw, Poland
3)Matériaux, Ingénierie et Sciences, University of Lyon, INSA-Lyon, UMR 5510 CNRS,
69621 Villeurbanne, France 4)
Institute of Science and Technology for Ceramics, CNR, 48018 Faenza, Italy 5)
Institute for Materials Research, Tohoku University, 980-8577, Sendai, Japan 6)
World-Lab Co., Ltd., 456-0023, Nagoya, Japan
The research activity on advanced laser materials is greatly increasing with the availability of
transparent sintered polycrystalline ceramics which present some advantages compared to
single crystals (sizes, mechanical strength, overall production cost). Single crystals are grown
from the melt, and they suffer from drawbacks such as segregation of the dopant from the
host, optical inhomogeneity caused by stress during crystal growth, high cost and low
productivity due to high temperature processing. Nowadays it is sometimes said that
polycrystalline ceramics are advantageous over single crystals in many ways [1].First, we will
present the evolution of laser materials from doped-single crystals to doped-ceramics mainly
from the pionner works of Japanese researchers as A. Ikesue [2] and H. Yagi [3]. Then, we
will introduce a few new results on different ceramics like layered YAG-Yb3+
:YAG structures
[4], Yb3+
-Er3+
-co-doped YAG
[5] and Lu2O3 fabricated by the non-conventional Spark Plasma Sintering (SPS) method [6].
Regarding more especially the important knowledge of the spatial distribution of rare earth
dopants in ceramics, we will give also our recent results on segregation phenomenon from
TEM technique associated with EDX probe. We have found a correlation between segregation
of rare earth dopants in YAG depending on their place in the lanthanide family: Nd3+
[7] and
Ce3+
[8-10], luminescent ions strongly segregate at grain-boundaries whereas Yb
3+ ions do not
segregate significantly [9, 11-12]. High Resolution and chemical spectroscopic nano-analysis
results indicate sometimes the presence of amorphous and crystalline silicate phases at grains
boundaries that could be one of the major scattering sources and the reason of the high optical
losses [13]. Contrary to YAG ceramics, segregation in sesquioxide ceramics does not seem
vary so drastically [11].
[1] G. Boulon, Optical Materials 34(3) (2012) 499-512.
[2] Ikesue, A.; Furusato, I.; Kamata, K. J. Am. Ceram. Soc. 78 (1995) 225–228.
[3] G. A. Kumar et al., IEEE J. Quantum Elecron. 40, no. 6, (2004) 747–758.
[4] L. Esposito et al., 13th ECerS Conference, Limoges 23-27 June 2013
[5] Jan Hostaša et al., 13th ECerS Conference, Limoges 23-27 June 2013
[6] G. Alombert-Goget et al., This Feofilov workshop.
[7] M.O. Ramirez et al., Optics Express 16(2008) 5966.
[8] W. Zhao et al., Jap. J. of App. Phys. 49 (2010) 022602.
[9] W. Zhao et al., Optical Materials 33 (2011) 684–687.
[10] G. Boulon et al., Jpn. J. Appl. Phys. 50, 9, Article ID: 090207, published on 2011/09/20
[11] T. Epicier et al., J. of Chem. Mater. 22 (2012) 18221-18229.
[12] V. I. Chani et al., Jpn. J. Appl.Phys. 49 (2010) 075601
[13] L. Esposito et al., J. European Ceramic Society 32(10) (2012) 2273– 2281.
76
We-2 Luminescence of lanthanide doped nanocrystals:
new systems, old theories and new opportunities
A. Meijerink, F. Rabouw, T. Senden, Y. Zhao, C. de Mello Donegá
Condensed Matter and Interfaces, Debye Institute for Nanomaterials Research, Princetonplein
5, 3584 CC Utrecht, The Netherlands, [email protected]
The present popularity of everything that involves ‘nano’ is not just a hype. In case of
semiconductor and metal nanoparticles new physical and chemical properties arise for sizes in
the nanometer regime. This results in fascinating size dependent optical and electrical
properties: the particles change color when the size is tuned in the nanometer regime. This
presentation will focus on nanocrystalline semiconductors (also known as quantum dots,
QDs) where quantum size effects are responsible for a change in the electronic structure in the
nanocrystals as a function of particle size. The incorporation of optically active dopants into
quantum dots and nanocrystals will be discussed. Doping luminescent lanthanide ions in
quantum dots give further control over the optical properties and to test theoretical models,
e.g. on the influence of refractive index on optical properties. Incorporation is however not
trivial. Several classes of lanthanide doped nanocrystals will be discussed, including II-VI
semiconductors like CdSe, CaS and SrS nanocrystals and LaPO4 insulators. Nanocrystals
doped with luminescent lanthanides are promising e.g. in the field of bio-medical, also using
afterglow or upconversion nanocrystals. In this presentation special attention will be given to
the influence of the refractive index on radiative decay rates and energy transfer. In Figure 1
the influence of the refractive index on the radiative decay rate is schematically depicted.
Careful measurements demonstrate that from the radiative decay rate in bulk LaPO4 the
radiative life time for Ce3+
and Tb3+
emission can be predicted for nanocrystals in solvents
with different refractive indices, without any adjustable parameters.
Figure 1 – Schematic representation of experiments on Ce and Tb doped nanocrystals used to
probe the influence of the refractive index on the radiative decay rate.
Nanocrystal:
LaPO4
Emitter:
Ce3+
or Tb3+
ion
Solvent
77
We-3 Hybrid Resonant Organic-Inorganic Nanostructures for Novel
Light Emitting Devices and Solar Cells
V.M. Agranovich
Institute of Spectroscopy, Russian Academy of Science, Troitsk, Russia
The strategy of integration of organic and inorganic semiconductors in a single nanostructure
may lead to many novel devices which take advantage of the good properties of both classes
of materials, overcoming the basic limitations of each individual class. Following this idea we
discuss properties of nanostructures based on combination of organic materials and inorganic
semiconductors, having respectively Frenkel excitons and Wannier-Mott excitons with nearly
equal energies. The resonant coupling between Frenkel and Wannier-Mott excitons in
quantum wells (or quantum wires or dots) may lead to striking novel effects: (i) strong
enhancement of the resonant all-optical nonlinearity in the strong coupling regime and (ii)
highly efficient energy transfer from inorganic quantum well to organic or inorganic material
in the weak coupling regime. The latter effect may be especially important for applications:
the electrical pumping of excitations in the semiconductor quantum well can be used to
efficiently turn on the organic material luminescence. We propose a new concept for light
emitting devices based on this effect. The efficient energy transfer in opposite direction,
namely from organic overlayer to quantum well or semiconductor nanocrystals can be used
for creation of new generation of solar cells. In a microcavity configuration the predicted and
observed giant polariton Rabi splitting drastically changes kinetics of luminescence and
conditions of the polariton condensation. Main time of talk will be used for demonstration the
most typical recently published experimental results obtained in Germany(Berlin),
UK(London) and in USA (MIT, Brown, An Arbor). These results indeed confirm that
combining organic and inorganic semiconductors leads to novel nanoscale design for light-
emitting, photovoltaic and sensor applications.
78
We-4 Spectroscopic Investigations on Glasses, Glass-ceramics and Ceramics
Developed for Nuclear Waste Immobilization
D. Caurant
Laboratoire de Chimie de la Matière Condensée de Paris (UMR CNRS 7574), Ecole
Nationale Supérieure de Chimie de Paris (Chimie-ParisTech), 75005 Paris, France
Highly radioactive nuclear waste solutions must be immobilized in very durable matrices in
order to avoid their dispersion in the biosphere. These wastes are chemically complex
mixtures of more than 40 elements that are incorporated today in the structure of durable
glasses such as borosilicates (Fig. 1). In the future, the wish to increase the waste loading in
glasses could induce their partial crystallization during melt cooling that must be avoided or
controlled. Moreover, it has been envisaged to selectively separate and immobilize in more
durable matrices - such as ceramics and glass-ceramics - several of the main long half-life
radionuclides (actinides, cesium) occurring in the waste solutions.
In this paper, we present spectroscopic investigations performed on different kinds of
matrices using various spectroscopic methods. For instance, the structure of borosilicate
glasses containing high lanthanide or molybdenum contents, their crystallization tendency
(Fig. 2) and their chemical durability against water have been studied by coupling optical
absorption, EXAFS, Raman and MAS NMR spectroscopic methods. On the other hand, the
specific incorporation of actinides (simulated in this work by non-radioactive lanthanides) in
the structure of very durable zirconolite-based (CaZrTi2O7) ceramics and glass-ceramics has
been studied by optical absorption and EPR spectroscopies. Finally, the -irradiation
resistance and thermal stability of the paramagnetic defects (Ti3+
and hole centers) induced by
electrons irradiation of a hollandite (Ba1.16Al2.32Ti5.68O16) ceramic able to incorporate
radioactive cesium have been studied by EPR. To explain the formation of these defects and
their evolution with temperature, a structural model has been proposed.
Fig. 1 (left) Schematic structural model of an aluminoborosilicate glass showing the incorporation of
Mo6+ and Nd3+ cations in regions rich in Na+, Ca2+ cations and non-bridging oxygen atoms. Fig. 2
(right) Scanning electron microscopy image of a partially crystallized glass containing
Ca2Nd8(SiO4)6O2 apatite crystals and evolution of its optical absorption spectra (Nd3+ 4I9/2 2P1/2
transition, T=10K) with heat treatment temperature.
40 µm
79
We-5 Micro-luminescence spectroscopy of Xe optical center in diamond:
production, structure and zero-phonon line broadening
Yury Deshko, Anshel Gorokhovsky
CUNY / The College of Staten Island and The Graduate Center, 2800 Victory Blvd.,
Staten Island, NY 10314, USA
E-mail: [email protected]
The current attention to the optical and the spin properties of impurity centers in
diamond is stimulated by recent progresses in understanding and applications of the nitrogen-
vacancy (NV) center [1]. Diamond possesses unique material properties, e.g. extreme
hardness, high thermal conductivity, wide band-gap, high Debye temperature,
biocompatibility, and photostability of defect centers. Due to these reasons, diamond is
considered as a potentially useful material for advanced photonics applications such as single
photon emitters and light emitting diodes, bioimaging and magnetosensing, quantum optics
and computing. Optical centers can be formed during diamond growth or by ion implantation
followed by thermal annealing. The latter method gives one control over the accuracy of the
spatial distribution of the implanted ions, as well as the dose of implantation and the type of
the implanted ion. Due to a variety of combinations of host materials and implanted ions, the
search for optical centers having suitable properties, supplementary to NV centers, is in
progress.
In this presentation we will review the photoluminescence and the spectroscopic
properties of diamond crystals implanted with Xe+ ions. The Xe-related optical center is of
particular interest, as it is one of a few centers (Ni, Si, Cr) in diamond having sharp zero
phonon emission lines (ZPL) in the infrared spectral region, specifically at 813 and 794 nm.
At low temperatures the photoluminescence spectra feature a single narrow ZPL at 811.7 nm
(in some crystals the linewidth is less than 0.2 cm-1
– similar to lines of RE ions in good
crystals) and a weak phonon sideband – the Debye-Waller is factor about 0.9. The following
topics will be discussed: formation of the Xe centers by ion implantation; implantation dose
dependence (1010
– 5x1014
ion/cm2) and Raman characterization; micro-luminescence
confocal mapping and the statistical approach to determine the conversion yield of implanted
ions into emitting centers; low and high temperature luminescence spectra; polarized
luminescence; mechanisms of inhomogeneous broadening of the ZPL; mechanisms of optical
vibrational dephasing; applications for diamond light emitting diode and nanofabrication.
[1] MRS BULLETIN. Nitrogen-vacancy centers: Physics and applications. Guest Eds. V.
Acosta, P. Hemmer. Vol. 38, No. 2 (2013)
80
We-6 Quantum spin-dynamics and decoherence examined in terms of
the “classical Landau-Zener model”
B. Barbara
Institut Néel, CNRS & UJF, Grenoble France
Mesoscopic physics is a sub-discipline of condensed-matter physics that focuses on the
properties of solids in a size range intermediate between bulk matter and individual atoms. In
particular, it is characteristic of a domain where a certain number of interacting objects can
easily be tuned between classical and quantum regimes, thus enabling studies at the border of
the two. Taking the example of mesoscopic spin systems, it is shown how quantum relaxation
can drastically reduce classical irreversibility on the basis of the Landau–Zener model.
A classical counterpart of this model is described enabling, in particular, intuitive
understanding of most aspects of quantum spin dynamics of ensembles of spin qubits and also
in other types of qubits such as a single spin in a quantum dot or a superconducting loop. As
in the molecular magnet V15, the leading decoherence terms of superconducting qubits seem
to be associated with a non-Markovian channel in which short-living entanglements with
distributions of two-level systems (nuclear spins, impurity spins and/or charges) leading to 1/f
noise induce T1-like relaxation with dissipation to the bath of two-level systems with which
they interact most. All these experiments on quantum oscillations are, most of the time,
performed in the classical regime of Rabi oscillations, suggesting that decoherence might also
be treated classically. This can be done in the framework of the «classical Landau-Zener
model».
81
We-7 Decoherence in the spin ensemble driven by microwaves
E.I. Baibekov
Kazan Federal University, 420008 Kazan, Russian Federation
Electron spin ensembles attract much attention in quantum information processing
because of their relatively long coherence times and potential for scalability [1]. Spin
manipulations necessary for quantum computation are achieved with proper adjustment of the
strength and duration of pulsed microwave field. Suppressing the decoherence in the spin
ensemble driven by microwaves still represents a challenging problem. We analyze possible
mechanisms of such “driven decoherence”, some of these mechanisms have no direct
analogues in the microwave-free regime. They are best described in terms of fluctuating
magnetic fields produced at the position of a given spin. The sources of these fields can be (i)
internal (dipole interactions between the spins of the ensemble), (ii) external (interactions
with the neighboring nuclear spins), or (iii) come directly from the interaction with the
microwave field.
The role of dipole interactions between the electron spins is analyzed in the framework
of Anderson’s statistical theory modified for the rotation reference frame. The corresponding
coherence times obtained in the continuum approximation are inversely proportional to the
spin concentration and depend on the microwave field strength [2].
The interaction of the electron spins with the nuclear spin bath represents the case
when the coupled spins have completely different resonance frequencies, and relatively long
coherence times are expected. However, Hartmann-Hahn polarization transfer boosts the
relaxation when the electron spin nutation frequency comes close to the nuclear spin
precession frequency [3].
Finally, the coupling of the electron spin ensemble with the resonant mode of a
microwave cavity will be discussed. At low temperature, the whole system is known to be in a
coherent spin-photon state that manifests itself by the splitting of the cavity mode frequency
(vacuum Rabi splitting [4]). This coherence is lost with the increase of temperature as the
splitting is gradually reduced and the split lines of the cavity emission spectrum are
broadened.
This work was supported by RFBR (grant no. 12-02-31336) and by Dynasty
Foundation. Author thanks Boris Malkin for advice and discussion of the results.
[1] D. Loss, D. P. DiVincenzo, Phys. Rev. A 57, 120 (1998).
[2] E. I. Baibekov, JETP Lett. 93, 292 (2011).
[3] J.H. Shim, S. Bertaina, S. Gambarelli, T. Mitra, A. Müller, E. I. Baibekov, B. Z. Malkin,
B. Tsukerblat, B. Barbara, Phys. Rev. Lett. 109, 050401 (2012).
[4] J.J. Sanchez-Mondragon, N.B. Narozhny, J.H. Eberly, Phys. Rev. Lett. 51, 550 (1983).
82
We-8 The nonlinear coherent spontaneous emission upon mixing
of the 2D-exciton material waves
V. V. Ovsyankin, B.V. Stroganov, A.V. Khilko,
Yu. K. Dolgikh, S. A. Eliseev, Yu. P. Efimov, and V.V. Petrov
Saint-Petersburg State University, Physics Department, 198504 Saint Petersburg, Russia
The experiments with Bose-Einstein (BE) condensate, remarkable in design and
outstanding in results, gave rise to a strong rise of interest to BE condensation of 2D excitons
in quantum-well structures. Practical interest to these objects is motivated by prospects of
application of the 2D quantum mirrors in the systems of parallel information processing. A
scientific intrigue of this story stems from fundamental prohibition of the BE condensation for
a uniform 2D gas at finite temperature due to its destabilization by thermal fluctuations
(Hohenberg’s theorem, [1]). The Hohenberg theorem excludes spontaneous coherence of the
2D multiexciton (MX) states which serves as the main criterion of achieving the BE
condensation in the commonly accepted experimental arrangement with the initial condition
“hot excitons – ultracold thermostat”. This theorem, however, does not forbid formation of
nonequilibrium coherent MX states excited by a short pulse of coherent resonant EM field.
For the ideal gas of 2D excitons in perfect QW structures, with the 2D exciton wave
vector q being a good quantum number, this statement is obvious. Under these conditions,
accessible for the optical excitation are the coherent MX excitations with arbitrary q from the
light cone |q|≤ ω/nc equal to in-plane components of the wave vectors of the exciting EM
field onto the QW plane (q = k||). In the mean-field description, the wave function of the MX
states generated in this way has the form of a classical field Фq(r,t) =
)]2
(exp[)(2
qρtm
qitnq
. Specifically, under condition of normal incidence of the exciting
pulse, optical excitation generates an MX state with q = 0, identical to the state of the BE
condensate at T = 0 K with Ф0(r,t) = )(0 tn . This scheme of generation of the excitonic
fields corresponds to the initial state “ultracold excitons – hot thermostat (UCX-HT)”, whose
temperature is limited from above by the condition of equality between the rates of thermal
decoherence and radiative annihilation of excitons.
The UCX-HT scheme perfectly fits the experiments on exciton-wave mixing, whose
detection will allow us to answer the nontrivial question about existence of the coherent MX
states in real QW structures with inevitable structural disorder. In the report, we present the
results of studying the resonant FWM on 2D excitons in a high-quality SQW structure
GaAlAs/GaAs/GaAlAs. In these studies, we have found two, previously unknown, processes
of the FWM signal formation, whose curious phenomenology is incompatible with the known
model of the FWM formation in structures of this kind. We show that the sources of the FWM
signal, in both cases, are the coherent MX states born due to mixing of the excitonic fields
created within the UCX-HT scheme. We propose mechanisms and mathematical models
leading to adequate description of regulations of each of the discovered processes of the 2D
exciton wave mixing. In conclusion, we discuss criteria of existence and temperature stability
of the nonequilibrium coherent MX states.
[1] P.C. Hohenberg, Phys.Rev. 158, 383 (1967)
83
Th-1 Magnetic excitations and magnetoelectric phenomena in the rare-earth borates
A.A. Mukhin, A.M. Kuzmenko, V.Yu. Ivanov
Prokhorov General Physics Institute of the RAS, Vavilov St. 38, 119991 Moscow, Russia
Rare-earth ferroborates RFe3(BO3)4 and alumoborates RAl3(BO3)4 are new family of
multiferroics possessing non-centrosymmetrical trigonal crystal structure and exhibiting
interesting magnetic, magnetoelectric, optical and other properties which strongly depend on
rare-earth (R) ions and its ground state in the crystal and exchange (R-Fe) fields. The low
energy crystal-field transitions and collective magnetic excitations in antiferromagnetic Fe-
subsystem (TN = 30-40 K) are to be responsible for the magnetic and magnetoelectric
properties of the borates. We have investigated these excitations in Tm, Ho… alumoborates
and Nd, Sm, Gd… ferroborates in the submillimeter (terahertz) frequency range 2-33 cm-1
using quasioptical backward-wave-oscillator spectrometer. Furthermore, magnetic and
magnetoelectric properties of the corresponding borates have been also studied and analyzed.
In the transmittance spectra of Tm and Ho alumoborates we observed several crystal-field
transitions at low temperatures at different polarizations of the radiation. Using selection rules
for the crystal-field transitions in D3 symmetry sites occupied by R3+
ions in the crystal we
have identified some of the observed transitions as magnetic dipolar or electric dipolar ones.
Temperature dependencies of the contributions to the permeability and permittivity of the
transitions have been obtained which are in a reasonable agreement with a behavior of static
magnetic and electric susceptibilities. The values of the corresponding matrix elements of the
observed transitions were also extracted by simulation of these data. The both alumoborates
exhibit significant electric polarization in magnetic field H, which can be represented for the
moderate fields by Px= α1HyHz + α2(Hx2- Hy
2) and Py= -α1HxHz - 2α2HxHy according to the
symmetry of the crystal, where α1, 2 are the quadratic magnetoelectric susceptibilities. We
have shown that observed dependencies of the electric polarization on the orientation of the H
are in a good agreement with these relations and thus Px, y are determined by α1,2, whose
experimental temperature dependencies were determined and corresponding theoretical
simulation were also performed. As a result we have carried out a self-consistent description
of the static magnetic, electric and quadratic magnetoelectric susceptibilities based on the
spectroscopic data for the alumoborates studied.
Resonance modes that are due to magnetic excitations in the exchange coupled
subsystems of rare earth ions (R = Nd3+
, Sm3+
, and Gd3+
) and Fe3+
ions have been detected in
the corresponding ferroborates [1]. The strong interaction between spin oscillations of the Fe
and R subsystems has been revealed, which determines the behavior of the modes depending
on the anisotropy of the exchange splitting of the ground doublet of the R ion. It has been
shown that the intensities of coupled modes (contributions to the magnetic permeability)
depend strongly on the difference between the g factors of Fe and R ions. This dependence
makes it possible to determine the sign of the latter g factor. In particular, a noticeable
intensity of exchange Nd modes in NdFe3(BO3)4 is due to an increase in their contribution at
g,||Nd
< 0, while in GdFe3(BO3)4 with gGd ≈ gFe ≈ 2, the Fe and Gd contributions compensate
each other and the exchange (Gd) mode is not observed. In spite of the weak interaction of
Sm ions with the magnetic field, SmFe3(BO3)4 exhibits resonance modes, which are attributed
to the excitation of Sm ions through the Fe subsystem. A giant dielectric effect and significant
electric polarization in SmFe3(BO3)4[2] are also determined by the Sm-Fe exchange coupling.
The work is partially supported by RFBR (12-02-01261, 12-02-31461 mol, 13-02-01093).
[1] A.M. Kuz’menko, A.A. Mukhin, V. Yu. Ivanov, et al., JETP Lett, 94, 294 (2011).
[2] A.A. Mukhin, G.P. Vorob’ev, V.Yu. Ivanov, et al., JETP Lett, 93, 275 (2011).
84
Th-2 Magnetic and magnetoelectric excitations in multiferroic rare earth manganites
A. Pimenov
Vienna University of Technology, 1040 Vienna, Austria
E-mail: [email protected]
Multiferroics are materials simultaneously showing ferromagnetic and ferroelectric order.
Two order parameters are coupled in these materials, which leads to such unusual effects like
magnetic switching of electric polarization and dielectric constant. As can be expected already
from the first principles, changes in the static properties of multiferroics must be accompanied
by dynamic effects like characteristic magnetoelectric excitations. Indeed, such excitations
could be recently observed in the spectra and were called electromagnons. Contrary to the
conventional magnons, the electromagnons are excited by the electric component of the
electromagnetic wave and contribute to the static dielectric permittivity. The suppression of
electromagnons in external magnetic fields provides a natural explanation for the
magnetoelectric effects in broad frequency range between dc and terahertz.
Fig. 1: Terahertz transmittance of TbMnO3 for
different experimental geometries. Upper and middle
panels: antiferromagnetic resonance modes. Lower
panel: transmittance for a geometry e||a with
electromagnons at 18 cm-1 and 26 cm-1. The
geometry of each transmittance experiment is given
in parentheses.
0.1
1
0 10 20 30
10-5
10-3
10-1
0.1
1
AFMR
h||b (e||c)
electromagnon
e||a (h||c)
(cm-1)
Tra
nsm
itta
nce
TbMnO3
T = 3 K
AFMR
h||c (e||b)
85
Th-3 Definition of odd symmetry crystal field parameters from optical spectra
A.A. Kornienko1)
, E.B. Dunina1)
, L.A. Fomicheva2)
1)
Vitebsk State Technological University, 210035, Vitebsk, Belarus 2) Belarusian State University of Informatics and Radioelectronics, 220013, Minsk, Belarus
E-mail: [email protected]
For description of Stark structure of multiplets of rare-earth ions in laser materials, the
crystal field theory is usually used. The investigation of optical spectra of high symmetry
systems has shown that the crystal field theory requires essential modification. The
microscopic and phenomenological models are improved practically independent on each
other. To improve the description, it is offered in Refs. [1] and [2] to take into account the
spin-correlated crystal field and the 4f12
np6/4f
13np
5 configuration interaction, respectively.
In this work, we report on an alternative improving of description by including the
interaction with excited configurations of opposite parity and covalent effects. The offered
method essentially extends opportunities of an optical spectroscopy allowing determination of
the odd symmetry crystal field parameters and covalent parameters. The applications of the
method are shown on example of Tm3+
ion in various crystals.
[1] J.R.G. Thorne et al, J. Phys.: Condens. Matter 13 (2001) 7403-7419.
[2] M.D. Faucher et al, J. Phys. Chem. A 108 (2004) 5278-5287.
86
Th-4 Series of phase transitions in IR-spectra of multiferroic TbMnO3
S. Klimin1)
, M. Kashchenko1,2)
, A.A. Nugroho3)
, P.H.M. van Losdrecht4a)
1)
Institute of Spectroscopy, Russian Academy of Sciences, 142190, Fizicheskaya 5, Troitsk,
Moscow, Russia 2)
Moscow Institute of Physics and Technology, 141700, Institutskiy lane 9, Dolgoprudny, Russia 3)
Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Indonesia 4)
Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen,
The Netherlands.
The rare-earth (RE) manganites RMnO3 show a strong interplay between lattice,
magnetic and charge degrees of freedom. TbMnO3 is recognized to be a canonical
multiferroic due to the strong correlation between magnetic order and spontaneous electric
polarization. The interest in these kind of systems is primarily driven by the potential of
multiferroics as promising materials for electronic components, for instance for the magnetic
recording or ferroelectric memory applications. In addition, there is no exact understanding of
the fundamental aspects of the magnetoelectric interaction. Therefore, it is very important to
study in detail the complex and rich phase diagrams observed in multiferroics and, in
particular, in TbMnO3.
The optical transmittance spectra of oriented single-crystal samples of TbMnO3 were
investigated over a wide spectral (1000 – 7000 cm-1
) and temperature (1.7 – 300 K) range.
The absorption spectra shows the relatively narrow lines of the 4f-4f transitions in the Tb3+
ions, and a broad absorption band originating from Mn3+
d-d transitions, and a strong
absorption edge due to the Mn3+
-O2-
p-d transitions. In addition to the stronger 4f-4f
transitions we have also observed a weaker 4f-4f spectrum which we attribute to the presence
of impurities (for instance due to deviations from the ideal oxygen stoichiometry). The
terbium and manganese occupy unique fourfold positions in the structure of TbMnO3 with Cs
symmetry for terbium and C1 - for manganese. The spectra show distinct changes at
temperatures corresponding to phase transitions in TbMnO3: TNMn
=42K, TFE=28K, and
TTb=7K. The magnetic ordering of the Mn sublattice at TNMn
is accompanied by a change of the
manganese d-d transitions. A narrowing and shift of broad Mn3+
bands leads to an increase of
transmittance in the 4000-5000 cm-1
frequency range. The spectral features of the 4f-4f terbium
transitions respond to the magnetic order by a weak line narrowing due to the appearance of the
internal magnetic field. More significant changes in the 4f-4f spectral features occur at
temperatures below TFE, where the spontaneous polarization arises [2]. The redistribution of
charge leads to a change of the crystal field (CF), and, consequently, to shift and splitting of the
spectral 4f-4f lines. Furthermore, the CF energies of the rare earth ion show an additional
significant shift at the terbium magnetic ordering temperature, TTb. This is in accordance with the
observed significant increase of spontaneous polarization. Using our data and a CF model we
have constructed the energy level diagram of the Tb3+
ions in TbMnO3, which does not only allow
us to understand the optical spectrum, but also gives a natural interpretation of the anomalous
behaviour of the low temperature thermal conductivity. Finally we note that we have not been
able to detect a Tb3+
transition at ~ 4.5 meV, which was reported in [3], in agreement with our CF
energy level scheme.
[1] D Meier et al., New Journal of Physics, 9 (2007) 100.
[2] T. Kimura et al., Nature, 426 (2003) 55.
[3] В. Seniff et al., J.Phys.:Condens. Matter 20 (2008) 434212 a Present address: II. Physikalisches Institut, University of Cologne, Germany. [email protected]
87
Th-5 Size effects in fluorescence of Сe3+
ions in nanocrystals
S.P. Feofilov
Ioffe Physical-Technical Institute, Polytekhnicheskaya 26, St. Petersburg, 194021, Russia
Cerium-doped YAG:Ce3+
, Sc2O3:Ce3+
and Y2O2S:Ce3+
are luminescent materials in which a
broad Ce3+
electron-phonon 4f05d
1–4f
1 electric dipole emission band occurs in the visible part
of the optical spectrum. We report the studies of new effects in fluorescence of
nanocrystalline (and crystalline) samples of these materials.
Two unusual effects of spatial confinement were observed in fluorescence of
nanocrystalline Ce3+
-doped materials:
(i) The dependence of Ce3+
ions fluorescence in YAG:Ce3+
and Sc2O3:Ce3+
nanoparticles on
the pressure of the gaseous media in which the nanocrystalline powder samples are placed
[1,2]. This effect was explained based on a model, involving Ce3+
two-photon
photoionization resulting in its conversion to Ce4+
followed by Ce3+
recovery assisted by the
surrounding gas molecules.
(ii) The temperature quenching of the fluorescence of Y2O2S:Ce3+
nanocrystals occurs at
lower temperatures than in micron sized particles. The experimentally observed steep drop of
fluorescence intensity with temperature may be explained by high-order multiphonon
relaxation. The temperature dependences of fluorescence intensity for nanocrystalline
samples are shifted by about 15 K towards lower temperatures. This difference directly
shows the existence of confinement effects in multiphonon relaxation which cannot be due to
modification of the phonon spectrum in nanoparticles [3].
One more striking effect (iii), that is observed in both nano- and single-crystal YAG:Ce
samples, is closely related to size effects in Ce3+
-doped nanoparticles. It was found [4] that
Ce3+
fluorescence is efficiently excited by photons with energies at least 1650 cm-1
below the
zero-phonon line (ZPL) of the 4f–5d transition, located at 489 nm, and the emitted spectrum
has a strong anti-Stokes component. The fluorescence spectra of Ce3+
were studied as a
function of temperature and excitation wavelength and their temporal evolution was
monitored. The mechanism of below-ZPL excitation of regular Ce3+
ions in the bulk and
nanocrystalline YAG samples is suggested, which includes a significantly nonequilibrium
nonradiative energy transfer from directly excited distorted Ce3+
centers to regular ones and
extraction of the necessary additional energy from the phonon reservoir.
The relation between the effects (i) and (iii) was studied experimentally. Differences were
found in the pressure-dependent behavior of the fluorescence of regular and distorted Ce3+
ions that result in changes of the fluorescence spectrum shape with the surrounding gas
pressure.
The dynamical processes in the excited state that are responsible for the observed effects are
discussed.
[1] S.P. Feofilov, D.V. Arsentyev, A.B. Kulinkin, T. Gacoin, G. Mialon, R.S. Meltzer, C.
Dujardin. J. Appl. Phys. 107, 064308 (2010).
[2] S.P. Feofilov, D.V. Arsentyev, A.B. Kulinkin, R.I. Zakharchenya. J. Lumin. 131, 438–441
(2011).
[3] S.P. Feofilov, A.B. Kulinkin, R.I. Zakharchenya, J. Hölsä, M. Malkamäki. Phys. Stat. Sol.
(b) 250, 249–253 (2013).
[4] S.P. Feofilov, A.B. Kulinkin, T. Gacoin, G. Mialon, G. Dantelle, R.S. Meltzer, C. Dujardin.
J. Lumin. 132, 3082 (2012).
88
Th-6 Luminescent characteristics of nanocomposites based on the doped nanoparticles
K. K. Pukhov
A.M. Prokhorov General Physics Institute RAS , 119991, 38 Vavilov Street, build. ‘4’,
Moscow, Russia. E-mail: [email protected]
The key problem of nanocomposites is to reveal physical reasons for changes in the
rate of spontaneous emission A of an optical center upon its displacement from a bulk
homogeneous material into a nanoparticle and to determine regular features of spontaneous
emission in the nanocomposite. (Here, the nanocomposite is considered to mean a medium
that contains nanoparticles as inclusions.) Knowing the probabilities of spontaneous
transitions allows one to obtain other luminescent characteristics of nanocomposites (e.g.,
regularities for the absorption and emission cross sections and threshold values of generation).
At present, for nanoparticles the linear size of which is much smaller than transition
wavelength λ, there are two main methods of modification of the expression A for
nanocomposites [1]. The first approach originates from groundbreaking work by Meltzer,
Feofilov, Tissue, and Yuan [2]. Here we present results of theoretical study of the
spontaneous emission rate based on another approach, which has been developed in our works
[3–8]. This second approach takes into account changes not only in the density of photon
states (so called Purcell effect [9]), but also in the amplitudes of zeropoint oscillations of the
electric field, which are responsible for the spontaneous decay.
[1] K. Dolgaleva, R. W. Boyd, Adv. Opt. Photon. 4 (2012) 1.
[2] R. S. Meltzer, S. P. Feofilov, B. Tissue, H. B. Yuan, Phys. Rev. 60 (1999) R14012.
[3] K. K. Pukhov, T. T. Basiev, Yu. V. Orlovskii, JETP Lett. 88 (2008) 12.
[4] K. K. Pukhov, J. of Rare Earths 27 (2009) 637.
[5] K. K. Pukhov, T. T. Basiev, Opt. Mater. 32 (2010) 1664.
[6] K. K. Pukhov, T. T. Basiev, Yu. V. Orlovskii, Opt. and Spectr. 111 (2011) 386.
[7] K. K. Pukhov, T. T. Basiev, Chang-Kui Duan et al, Opt. and Spectr. 114 (2013) 868.
[8] K. K. Pukhov, T. T. Basiev, Opt. Mater. (2013) In press.
[9] E. M. Purcell, Phys. Rev. 69 (1946) 681.
89
Th-7 Enhancement of the nonlinear response and spontaneous emission
of Nd3+
doped LiNbO3 by silver nanoparticles
L. E. Bausá, E. Yraola, P. Molina, M.O. Ramírez
Dept. Física de Materiales, Universidad Autónoma de Madrid, 28049-Madrid, Spain
Metallic nanostructures are attracting great interest because they provide mechanisms for
tailoring and manipulating local optical electric fields in a sub-wavelength domain.
Here, periodical arrays of Ag nanoparticles are self-assembled on Nd3+
doped periodically
poled ferroelectric laser crystals. The coupling between the optical transitions of Nd3+
ions
and the localized surface plasmon resonances supported by the metallic nanostructures results
in a periodic intensification of the spontaneous emission at the Nd3+
laser wavelength of
around 80 %. The mechanism of enhancement is analyzed considering different polarization
configurations. Additionally, taking into account the nonlinear character of LiNbO3 crystal,
the interaction between the metallic nanoparticles and the second harmonic generation is also
studied to demonstrate a remarkable intensification of the quadratic nonlinear response, in a
factor of 20, which takes place with the periodicity of the metallic arrays.
The results are of interest for the design of submicrometric lasers or gain-enhanced
metamaterials.
90
Th-8 Spectral Properties of ME – RE Ions in Quasi-Ordered Nano-Structures
on Oxide Surface
N. A. Kulagin
Ukrainian with Germany Joint Venture “Firma SIFA”, 61045 Kharkov, Ukraine.
E-mail:[email protected].
Relations of spectral properties, crystallographic structure, and properties of nano-scale size
crystallites on the surface of selected pure and doped with Me/RE/AC ions oxide single
crystals before and after plasma treatment were studied on the base of experimental and
theoretical approach [1, 2]. The main efforts focused on study of electronic structure of the
systems of ordered one- and two level crystallites with size of about 10-6
– 10-10
m raised on
the oxide surface after treatment in compression plasma flow [1].
a) b)
Figure 1. Nano-crystalline structures on the surface of SrTiO3 – a) and sapphire – b)
single crystals after plasma treatment
Results of study of the bulk crystals and surface of the samples before and after plasma
treatment by spectral (optic and ESR of near surface layers) and AFM, SEM, TEM
techniques, XRD analysis and high resolution X ray spectroscopy method have been
presented, too[2-3]. Nature, electronic, spectral and crystallographic structure of nano-scale
samples were explained in the frame work of self-consistent theory of electronic structure of
clusters [4].
Novel nano-scale size structures may be effectively used as materials and objects for new
laser materials, scintillators and electronic devices.
[1] Physics of Laser Crystals. Eds. J.-C. Krupa, N. A. Kulagin. Kluwer Academic
Publisher. Brussels. 2003
[2] N.A. Kulagin. J. Quant.Electr. 42 (2012) 1008
[3] N.A. Kulagin, J. Dojcilovic, E. Hieckmann,. MSA 2 (2011) 126
[4] N.A. Kulagin, D.T. Sviridov. Methods of Calculation for Electronic Structure of Free
and Impurity Ions. Moscow. Nauka. 1986 [in Russian]
91
Th-9 Determination of energies of localized states related to Ln3+
and Ln2+
ions
with respect to bandgaps of the host by high pressure spectroscopy
M. Grinberg
Institute of Experimental Physics, University of Gdańsk, Wita Stwosza 57, 80-952 Gdansk,
Poland
E-mail :[email protected]
Rare earth ion dopands create the luminescence centers in solids. The emission takes
place usually due to internal transitions of 4fn4f
n and 4f
n-15d
14f
n types. The emission can
be excited due to internal absorption (4fn 4f
n-15d
1 transition), charge transfer transition (CT)
or ionization process. In two last cases the fundamental for effective excitation energy
transfer from lattice to impurity are the intermediate states called impurity trapped exciton
(ITE) states that created by Coulomb potential of the carrier captured at the Impurity. In this
contribution the spectroscopic investigation of luminescence materials doped with several
ions: Ln3+
( Ce3+
, Pr3+
, Eu3+
) and Ln2+
(Eu2+
) are presented. The leading unique experimental
technique was high pressure spectroscopy where high hydrostatic pressure is applied in
diamond anvil cell (DAC). High hydrostatic pressure compresses the materials lead to
increase of interaction Ln ion with lattice. This allows to change energies of the of the ground
states of Ln3+ and Ln2+ ions with respect to bands edges of the host as well as the energies of the
excited states belonging to the excited electronic manifold 4fn-1
5d1
with respect to the ground
states of Ln2+(3+)
ions. Depending on the relative energy of the excited states of the Ln2+(3+)
ions with respect to the band edges pressure can quench or stimulate of the Ln2+(3+)
ions
luminescence.
Therefore high pressure is considered as very effective tool for investigation of
influence of ITE states on energy transfer processes in phosphors with Ln3+ and Ln2+ ions as
well as determining of energies of the ground states of the Ln2+(3+)
ions . The lecture presents the
review of last results on high pressure spectroscopy of Ce3+
, Pr3+
, Eu3+
and Eu2+
doped oxide
and fluoride phosphors.
92
Th-10 Rare earth oxide and orthovanadate up-conversion nanoparticles:
Synthesis and emission properties
Miroslav D. Dramićanin
Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
E-mail:[email protected]
Interest in rare-earth (RE) doped materials that exhibit emission via up-conversion (UC,
frequency conversion) has become notable because of their use in a wide range of
applications, from solid compact laser devices operating in the visible region and infrared
quantum counter detectors to next-generation lighting or displays, temperature sensors and
biological fluorescence. In addition, UC nanoparticles are of significant interest for
applications in two-photon bio-imaging, sensitive luminescent bio-labels, solar cells and
GaAs-coated highly efficient light emitting diodes (LED’s). Even though less efficient
compared to fluorides, oxide based UC materials are valuable due to their excellent chemical
and thermal stability. Rare earth sesquioxides and orthovanadates, with the general formula
A2O3 and AVO4 (A = Y, Gd, Lu) have been extensively studied for a long time for phosphor
applications. Due to the similar ionic radii, electronic structures and electronegativities
yttrium, gadolinium or lutetium ions can be replaced easily with the activator rare earth
(RE3+
) ions (Yb3+
, Er3+
, Ho3+
, Tm3+
, Nd
3+ or Pr
3+), in a wide range of concentrations, without
strongly affecting the lattice structure.
In this lecture static and dynamic luminescence spectroscopy of UC sesquioxide and
orthovanadate nanoparticles are presented. Comparison of spectral data with those from bulk
materials is given and discussed regarding particle size, crystallinity and ligand concentration
on nanoparticle surface. Color tuning of UC emission by changing of one or more activator
and sensiter ion concentrations is demonstrated by spectroscopy and explained in terms of
altered excitations and transitions mechanisms of rare earth ions. Effects of UC nanoparticles
co-doping with alkali metal ions (like enhancement of UC emission intensity, color tuning,
changes in lifetimes) are highlighted. At the end, brief insight into use of luminescence
spectroscopy of UC nanoparticles for temperature measurements is presented.
93
Th-11 Multiphonon relaxation accelerated by energy migration
in the hydroxylated rare-earth doped nanoparticles
Yu. V. Orlovskii1,2)
, A. V. Popov1,2)
, A. S. Vanetsev1)
, I. Sildos1)
1)
Institute of Physics, University of Tartu, 51014, 142 Riia str., Tartu, Estonia
E-mail: [email protected] 2)
General Physics Institute RAS, 119991, 38 Vavilov str., Moscow, Russia
We study the regularities of fluorescence kinetics I(t) in the hydroxylated rare-earth (RE)
doped nanoparticles when the OH- molecular groups act as a fluorescence quencher. They
may be either associated with the oxygen vacancies as in the Nd3+
doped Y2O3 nanoparticles
of monoclinic phase with mean diameter 12 nm [1] synthesized by laser ablation of solid
targets with subsequent recondensation in flow of air at atmospheric pressure [2] or can be a
part of a crystal structure as in the YPO4·0.8H2O:Ce3+
nanocrystals with D ≈ 40 nm
synthesized by the microwave-hydrothermal technique. We show that for the low
concentrations (0.1 – 0.2 at.%) of rare-earth dopant the fluorescence quenching occurs as a
result of direct multiphonon relaxation over the OH- vibronic levels with the order of the rate
determined by the order of the rate of spontaneous emission transitions in RE3+
participating
in the cross-relaxational nonradiative dipole-dipole energy transfer from RE3+
to OH-. It can
be either microsecond (dipole forbidden 4f-4f transitions in Nd3+
) [3] or nanosecond (dipole
allowed 5d-4f transitions in Ce3+
). In this case regardless of the quenching rate the kinetics of
impurity quenching is described by Förster equation
(1) 0( ) exp( )AN t t , where γA is the macroparameter of RE
3+ - OH
- energy transfer [4].
However, for the higher concentrations of RE3+
(1 – 2 at.%) the kinetics accelerates by RE3+
-
RE3+
dipole-dipole energy migration with subsequent RE3+
- OH- quenching. For the latter the
first time in a solid-state impurity laser media we observe non-stationary kinetics of impurity
quenching starting from Förster decay and ending with fluctuation kinetics of fluorescence
hopping quenching. The latter characterizes excitation decay in the regions depleted in donors
(RE3+
) and acceptors (OH-) determined by the kinetics of the Förster type with the increased
decay decrement
(2) 1
( ) exp( ( ) )f A DN t t
[5], where γD is the macroparameter of Nd-Nd energy
migration and α = γA / γD close to unity.
Regardless of the quenching rate the fluctuation kinetics of hopping fluorescence quenching
starts earlier than that expected from the theory in the bulk crystal due to the limited geometry
of NPs. This may lead to lower fluorescence quenching and to higher fluorescence quantum
yield.
This work is supported by European Social Fund (Grants #MTT50 and MJD167) and RFBR
grant #11-02-0248.
References
[1] J. Dhanaraj et al., J. Phys. Chem. B 105, 11098 (2001).
[2] V. V. Osipov et al., Laser Phys. 16, 116 (2006).
[3] Yu.V.Orlovskii, et al., J. Luminescence. 139, 91 (2013)
[4] Th. von. Förster, Ann. Phys. 2, 55 (1948); Ztschr. NaturForsch. A 4, 321 (1949).
[5] S. G. Fedorenko et al., Phys. Rev. B 48, 7020 (1993).
94
Th-12 Structure, spectroscopic and luminescent properties of Y(P,V)O4:Er
nanophosphors
S.A. Antoshkina1)
, P.A. Ryabochkina1)
, A.S. Vanetsev2)
, O.M. Gaitko3)
, S.N. Ushakov4)
,
A.V. Malov1)
, A.A. Panov1)
1) Institute of Physics and Chemistry, Ogarev Mordovia State University, 430005,
Bolshevistskaya Street 68, Saransk, Russia
2) Institute of Physics, University of Tartu, 51014, Riia 142, Tartu, Estonia
3) Moscow State University, 119991, Leninskie Gory 1-3, Moscow, Russia
4) Prokhorov Institute of General Physics RAS, 119991, Vavilov Street 38, Moscow, Russia
Development of synthesis methods and study of the physical characteristics of
nanomaterials are most important tasks of fundamental science and applications. Among the
variety of such objects luminescent materials based on nanocrystalline compounds activated
by rare earth (RE) ions currently attract special interest. This is due to the possibility of the
effective use in the production of fluorescent lamps, displays, CRT screens, and also for
biological and medical applications.
Compounds based on yttrium orthophosphate and yttrium orthovanadate doped by RE
ions have simultaneously morphological homogeneity and the effective luminescence in a
predetermined wavelength range. That allows using them as effective crystal phosphorus.
Furthermore, relatively simple synthesis methods and the higher photostability compared with
organic compounds provide the possibility of using them as biological markers.
In this work we report the results of study of nanocrystalline powders YPO4:Er
(CEr=1; 5 mol. %), YPO4:Yb,Er with tetragonal structure, YPO4∙0,8H2O:Er (CEr=1;
5 mol. %); YPO4∙0,8H2O:Yb,Er with hexagonal structure and YVO4:Er, which have been
synthesized by microwave-hydrothermal treatment.
To clarify the phase composition of the synthesized nanopowders X-ray diffraction
analysis has been performed. Comparison of the diffraction patterns for studied samples with
reference samples from the database PDF2 showed that samples of anhydrous
orthophosphates correspond to the phase of yttrium orthophosphate with a tetragonal structure
of xenotime, and samples of hydrate of yttrium orthophosphate correspond to the
YPO4∙0.8H2O phase with rhabdophane-like structure. Sample of orthovanadate YVO4:Er
correspond to the structural type of zircon. Using Scherrer equation mean size of coherent
scattering region have been estimated for samples YPO4:Er (CEr=1; 5 mol. %), YPO4:Yb,Er,
YPO4∙0,8H2O:Er (CEr=1; 5 mol. %), YPO4∙0,8H2O:Yb,Er и YVO4:Er. Obtained values
correlate well with values of mean size of particles calculated from SAXS curves.
Diffused reflection spectra of tetragonal YPO4:Er, hexagonal YPO4∙0,8H2O:Er and
YVO4:Er have been registered. Absorption bands corresponding to transitions from Er3+
ion 4I15/2 ground level to excited multiplets
4I13/2,
4I11/2,
4I9/2,
4F9/2,
4S3/2,
2H11/2,
4F7/2,
4F5/2,
4F3/2,
2H9/2,
4G11/2 have been identified for nanocrystalline YPO4:Er, YPO4∙0,8H2O:Er and YVO4:Er
(CEr=5 mol. %) from the obtained spectra.
Also we have obtained luminescence spectra for Er3+
ion due to 4I13/2→
4I15/2 transition
with excitation of 4I11/2 (λex=970 nm) for studied samples. It should be noted that
luminescence from the levels 4S3/2,
4F9/2,
4I11/2 of Er
3+ ions with excitation of
4S3/2 (λex=532
nm) has not been obtained in studied nanoscale crystalline particles. This fact we associate
with effective nonradiative energy transfer between Er3+
ions and OH- groups. For the same
reason, in our opinion,we were unable to register any luminescence of Er3+
ions from the
levels 4S3/2,
4F9/2 with excitation of
4I11/2 in nanopowders YPO4:Er, YPO4:Yb,Er, YVO4:Er
which is observed in bulk crystal with Er3+
and due to the interaction of excited Er3+
ions.
95
Th-13 Bulk, fibercrystal and nanocomposite scintillation materials
B.V. Shulgin1)
, I.N. Ogorodnikov1)
, L.V. Victirov1)
, A.N. Tcherepanov1)
, A.V. Ishchenko1)
,
V.Yu. Ivanov1)
, I.N. Sedunova1)
, V.L. Petrov1)
, T.S. Koroleva2)
, M.M. Kidibaev2)
,
C. Pedrini3)
, K. Lebbou3)
1)Ural Federal University, 620002, Mira str., 19, Yekaterinburg, Russia
2)Institute of Physical and Technical Problems and Materials Science of NAS KR, 720071,
Chuy 265a Bishkek, Kyrgyzstan 3)
University Claude Bernard Lyon 1, 69100, 43 Boulevard du 11 Novembre 1918,
Villeurbanne, France
E-mail: [email protected]
A short review of history early (from 1968) and some results of recent developments of
bulk (crystal, ceramic and glass), fibercrystal, nanocomposite scintillation detector materials
doped with rare earth elements are presented. The some scintillation properties: emission
maximum, light output (for some compounds absolute light yield), energy resolution, kinetic
properties and decay constant for investigated materials and the models of scintillation
processes are presented and discussed.
The new [1, 2] bulk and fibercrystal scintillation detector materials have been developed as
a rule on the base of oxide and fluoride compounds. For example for registration of neutrons
the fiber crystals LGBO and LYBO have been elaborated.
Some new nanocomposite inorganic-organic scintillation materials have been developed
on the base of inorganic BaF2, ZnO and ZnS fillers and high transparent epoxy and
polyurethane compounds for simultaneous registration of gamma rays and neutrons and some
new organic-organic composition with emissions bands at green-orange region 512–580 nm,
which convenient for PIN photodiode registration.
All results have been received due to collaboration efforts of Moscow (groups of
A.M. Prokhorov, V.V. Osiko, Kh.S. Bagdasarov, K.V. Solntsev et al), St. Petersburg (groups
of P.P. Feofilov, A.I. Ryskin et al, Ural (Ural school of luminescence and radiation physics),
Siberian (Tomsk, Novosibirsk, Irkutsk) and some foreign science centers in England
(Durham, K.N.R. Taylor), Kyrgyzstan (Bishkek, A. Alybakov), France (Lyon, C. Pedrini,
K. Lebbou), USA (Memphis, D.W. Cooke and Tuscalusa, Ch. Alexander), Japan (Tsukuba,
KEK-center, M. Kobayashi) and other Russian and foreign centers.
On the base of scintillation materials some new detector devices have been proposed [1, 2].
References
[1] B.V. Shulgin, A.N. Tcherepanov, L.V. Victirov, V.Yu. Ivanov, V.L. Petrov. New optical
materials and devices. Patent documents. Reference book. Editor prof. V.S. Kortov.
Yekaterinburg, UrFU. 2011. 691 p. (in Russian).
[2] B.V. Shulgin, V.Yu. Ivanov, V.L. Petrov. A.V. Ishchenko, A.N. Tcherepanov, Detector
materials and devices. Radiation technologies. Patents of Experimental Physics Departments
of UrFU (for 2007–2012 years). 2012. 359 p. (in Russian).
96
Th-14 VUV spectroscopic study of rare earth impurity trapped and regular excitons
in fluorides by synchrotron radiation
K. V. Ivanovskikh1)
, R. B. Hughes-Currie1)
, A. J. Salkeld1)
, M. F. Reid1,2)
,
J.-P.R Wells1)
, A. Meijerink3)
, R. J. Reeves1,2)
1) Department of Physics and Astronomy, University of Canterbury, Private bag 4800, 8140
Christchurch, New Zealand 2)
MacDiarmid Institute for Advanced Materials and Nanotechnology, PO Box 600, 6140
Wellington, New Zealand 3)
Debye Institute for NanoMaterials Science, University of Utrecht, PO Box 80000, 3508 TA
Utrecht, The Netherlands.
E-mail: [email protected]
Charge transfer process between the rare earth (RE) impurity and the host conduction band
may result in formation of stable photoionization states of RE ions known as impurity-trapped
excitons (ITEs). The formation of such an exciton is favoured when the valence state of the
RE ion is stable after photoionization. The formation of ITEs has been evidenced for some
divalent and trivalent ions in a number of fluoride and oxide hosts [1-3]. Structure of the ITEs
and intra-excitonic transitions have been recently studied in [4, 5].
It is important to understand processes leading to the formation of ITEs via energy transfer
from intrinsic (host) electronic excitations (regular excitons and e-h pairs). To this end we
performed time-resolved measurements of excitation and emission spectra as well as decay
kinetics of ITE emission in Yb2+
doped CaF2 and NaMgF3 under excitation with VUV (3.7 -
21 eV) synchrotron radiation in a wide temperature range. The VUV excitation spectra
revealed efficient host-to-Yb2+
energy transfer, which is dominated by the excitonic
mechanism at helium temperature and becomes complex at higher temperature. Analysis of
the spectral features related to 4f14
-4f13
5d transitions of the Yb2+
, which appear below the
band-to-band transitions have been performed employing a semi-empirical parametrised
crystal-field model, providing information on the interaction of the Yb2+
5d states with the
crystal ligands.
Fig. 1. Excitation spectra for self-trapped excition (STE) and ITE emission bands in CaF2:Yb2+ and
NaMgF3:Yb2+ at T = 7 K.
[1] B. Moine, B. Courtois, C. Pedrini, J. Phys. France 50 (1989) 2105.
[2] P. Dorenbos, J. Phys. Condens. Matter 15, (2003) 2645.
[3] C. Pedrini, A. Belsky, K.V. Ivanovskikh, et al. Chem. Phys. Lett., 515 (2011) 258-262.
[4] M. F. Reid, P. S. Senanayake, J.-P. R. Wells, et al. Phys. Rev. B 84, (2011) 113110.
[5] P. S. Senanayake, J.-P. R. Wells, M. F. Reid, et al. App. Phys. Lett. 100 (2012) 041902
4 6 8 10 12 14 16 18 20
CaF2:Yb
2+
Inte
nsi
ty (
a.u.)
Energy (eV)
ITE
STE
4 6 8 10 12 14 16 18 20
ITE
STE
NaMgF3:Yb
2+
Energy (eV)
97
Th-15 Luminescence of YAG doped with Eu, Yb and Mn ions under VUV excitation
N. M. Khaidukov1)
, V. N. Makhov2)
1)N. S. Kurnakov Institute of General and Inorganic Chemistry, 119991, 31 Leninskii
Prospekt, Moscow, Russia 2)
P. N. Lebedev Physical Institute, 119991, 53 Leninskii Prospekt, Moscow, Russia
At present, one of the rapidly developing fields of research in the phosphor technology
is designing new efficient phosphors for white-light lamps based on using light emitting
diodes (LED). Most phosphors proposed for white LED lamps are efficiently excited by a
blue LED and emit in the visible spectral range due to allowed interconfigurational 4f5d
transitions in Ce3+
, Eu2+
or Yb2+
ions. In the standard design of the white LED lamp the well-
known yellow phosphor Y3Al5O12:Ce3+
(YAG:Ce) is used. The disadvantages of such white
LEDs are a poor color rendering index and a high color temperature due to a lack of a red
spectral component. Thus, there is a need to develop bi-color phosphors having additional
emission in the red spectral range. The efficient red emission under blue LED excitation can
be obtained from Mn2+
, Mn3+
or Mn4+
in hosts having garnet structure [1] codoped with Ce3+
provided that there is an efficient energy transfer from Ce3+
to Mn ions. Also, data concerning
spectroscopic properties of Eu2+
and Yb2+
in YAG would be very useful for designing
phosphors in general and LED phosphors in particular. Although luminescence properties of
Ce3+
in YAG are now well enough understood, the properties of Eu2+
and Yb2+
as well as of
Mn ions in YAG were only randomly investigated (see, e.g. [1,2]). In the present work
luminescence properties of YAG doped with Eu, Yb and Mn ions were studied in order to
check the potential of using these ions as possible dopants in YAG-based phosphors for white
LEDs. For synthesizing ceramics of YAG doped with Eu or Yb ions the high-temperature solid
state reactions under reducing carbon monoxide conditions were carried out by using precursors
synthesized under hydrothermal conditions. The powder samples of YAG doped with Ce3+
and Mn3+
were synthesized under hydrothermal conditions in the presence of CeO2 for the
stabilization of the trivalent state of manganese. The measurements of emission (200-1200 nm)
and excitation (50-330 nm) spectra were performed at room and liquid-helium temperatures
under UV/VUV synchrotron radiation excitation. No any indications on the existence of
luminescence due to 5d-4f transitions of Eu2+
or Yb2+
in the synthesized YAG ceramics were
detected. The usual explanation of a lack of this luminescence is that the energy positions of
the lowest 4fn5d levels of these divalent ions in YAG are above the bottom of the host
conduction band, which leads to ionization of these ions after excitation to 4fn5d levels.
However, due to the large difference in crystal chemical properties between Eu2+
or Yb2+
and
Y3+
it is not clear whether these divalent ions can be introduced into the YAG matrix in
noticeable concentrations. On the other hand, the spectra show the presence of trivalent ions
Eu3+
and Yb3+
having characteristic narrow-line emissions in the red and IR regions,
respectively. The Mn-doped sample shows the broad-band emission with maximum at ~600
nm at both room and low temperature, which does not correspond to luminescence properties
of Mn3+
described in the literature. Also, no any narrow-line emissions were detected in the
red (~650-680 nm) or IR (~1100 nm) regions which could be attributed to characteristic
luminescence of Mn4+
or Mn3+
, respectively, according to the literature. Anyway, one should
take into account that Mn2+
and Mn4+
ions cannot be incorporated into YAG under
hydrothermal conditions due to crystal chemical differences between these ions and host ions
in YAG. Emission spectrum of Ce3+
/Mn codoped YAG is very similar to that of YAG singly
doped with Mn, which indicates that there is an efficient energy transfer from Ce3+
to Mn
ions. [1] K. Petermann, G. Huber, J. Lumin. 31&32, 71 (1984)
[2] M. Henke, J. Perßon, S. Kück, J. Lumin. 87-89, 1049 (2000).
98
Th-16 4fn-4f
n−15d line broadening in absorption spectra of Ce
3+, Pr
3+, Tb
3+ in CdF2
E. A. Radzhabov1,2)
1)Institute of Geochemistry RAS, 664033 Favorsky St. 1a, Irkutsk, Russia
2)Irkutsk State University, Physics dept, 664003 Gagarin boulevard 20, Irkutsk, Russia
E-mail: [email protected]
Spectroscopy of f-d transitions of rare-earth ions doped into crystals remains relatively less
investigated field of optical spectroscopy. The 5d orbitals are much more extended then 4f
orbitals and their interaction with lattice is much stronger. As the result the absorption or
excitation 4fn-4f
n-15d spectra (hereafter 4f-5d) consist of both zero-phonon lines and broader
vibronic bands. The fine structure of spectra was commonly seen in low energy side. The fine
structure usually disappears for transition to higher-energy 4f-5d states. This is attributed to
line broadening associated with the interaction of d-states with states of conduction bands of
the same energy [1,2]. To our knowledge no investigation of line broadening of 4f-5d
trivalent rare earth ions in CdF2 have been made.
Crystals were grown in vacuum in a graphite crucible by the Stockbarger method. Impurity of
rare-earth trifluoride in concentration of 0.01, 0.1 or 1 mol. % were added into the melt.
Absorption spectra were measured with Perkin-Elmer Lambda 950 spectrophotometer at
temperatures near 8K.
Absorption spectra of undoped CdF2 show fundamental absorption edge near 200 nm at room
temperature, the edge was shifted to near 185 nm at low temperatures. The absorption spectra
due to allowed 4f-5d transitions of Ce3+
, Pr3+
and Tb3+
were measured. The 4f-5d absorption
band of other rare-earth ions are at wavelength lower than 180 nm and could not be observed
in CdF2.
Absorption spectra of doped CdF2, CaF2, SrF2 and BaF2 samples due to 4f-5d transitions of
Ce3+
, Pr3+
and Tb3+
were measured with spectral resolution of 0.1-0.05 nm at 8K. The main
difference between spectra of CdF2 and other alkaline-earth fluorides is that the spectra of
CdF2 contains no fine structure. The absorption spectra of Ce3+
and Pr3+
in alkaline-earth
fluorides contains a number of sharp lines while the spectra become smooth in CdF2. The
spectra become quite similar if the spectra of alkaline-earth fluorides are broadened using
gaussian filter with width near 60-70 cm-1
. Apart to this the sharp lines of 5d-4f absorption of
Tb3+
in CaF2 become broader in a row of SrF2, BaF2, CdF2. It seems the position of 5d(eg)
level of Tb3+
ion is very close to bottom of conduction band in SrF2, BaF2. This is contradict
with the estimation of 5d(eg) positions of Tb3+
in alkaline-earth fluorides [3]. Undoubtedly,
the 5d(eg) levels of Ce3+
, Pr3+
, Tb3+
in CdF2 are well above the bottom of conduction band and
the broadening of the 4f-5d lines is due to the electron autoionization from 5d(eg) to
conduction band states.
[1] R. L. Fuller, D. S. McClure, Determination of photoionization rates of divalent samarium
doped in alkaline earth fluorides, Journal of Luminescence 1990, 45, 354 - 356
[2] C. Dujardin, B. Moine, C. Pedrini, One- and two-photon spectroscopy of f-d and f-f
transitions of Eu2+
ions in M1-xNxF2 mixed fluoride crystals (M, N = Ba, Sr, Ca; 0 <x< 1),
Journal of Luminescence 1993, 54, 259 - 270.
[3] P. A. Rodnyi, I.V. Khodyuk, G.B. Stryganyuk, Location of the energy levels of the rare-
earth ions in BaF2 and CdF2, Physics of the Solid State, 2008, 50, 1578–1581
99
Fr-1 The annealing of PrF3 nanoparticles by microwave irradiation
E.M.Alakshin, R.R. Gazizulin, A.V. Klochkov, S.L. Korableva, А.М. Sabitova, Т.R. Safin,
К.R. Safiullin, M.S. Tagirov.
Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russia
Over the last few years PrF3 nanoparticles have been widely investigated by our group
[1-5]. In present work the effect of microwave radiation on the restructuring of nanoscale
crystalline PrF3 powders were researched using nuclear magnetic resonance (NMR), nuclear
pseudo quadrupole resonance (NPQR) and high-resolution transmission electron microscopy
(HRTEM) methods. It was found that the relaxation times T1 of the 141
Pr and the 19
F nuclei
increase along with a duration time of microwave irradiation (Fig. 1), and the line width of
the 141
Pr spectrum become narrower (Fig. 2). The HRTEM results testify the influence of
microwave irradiation time on the size and shape of the PrF3 nanoparticles.
0 100 200 300 400 5000,0
0,9
1,8
2,7
3,6
0
30
60
90
120
150 141
Pr H0 = 120 mT
(left scale)
T1,
ms
Time of microwave irradiation, min
T = 1.5 K
19
F H0 = 170 mT
(right scale)
100 200 300 400 500 600 700 800
19.5 MHz
T=1,5 K
B0, mT
Inte
nsi
ty (
a.u
.)
micro PrF3
nano PrF3#2
nano PrF3#5
Fig.1 Relaxation time T1 of
141Pr and
19F in
PrF3 nanoparticles
Fig.2 NMR spectra of micropowder PrF3 and
nanopowder samples 2 and 5
Fig.3 HRTEM images of PrF3 nanoparticles (samples 1, 2 and 5)
As a result the influence of microwave irradiation on PrF3 nanoparticles structure was
investigated
[1] M.S. Tagirov, E.M. Alakshin, R.R. Gazizulin et al., J.Low Temp.Phys., 162, 645 (2011).
[2] Е.M. Alakshin, A.S. Aleksandrov, A.V. Egorov et al., JETP Lett., 94, 3,259 (2011).
[3] E.M. Alakshin, D.S. Blokhin, A.M. Sabitova et al., JETP Lett. 96,3 (2012).
[4] L.Ma, W. Chen, Y. Zheng, et al., Mater. Lett. 61, 2765 (2007).
[5] E.M. Alakshin, B.M. Gabidullin, A.T. Gubaidullin et al., arXiv:1104.0208 (2011).
100
Fr-2 EPR, optical and dielectric spectroscopy of Er ions doped cerium dioxide
nanoparticles
V.V. Pavlov, V.V. Semashko, R.M. Rakhmatullin, I.N. Kurkin
Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russian Federation
EPR, fluorescence spectra, and dielectric spectroscopy of Er3+
ions in CeO2 nanoparticles
with grain sizes of 22 and 300 nm were studied. The work was motivated by the potential
application of nano ceria in solid oxide fuel cells, catalysis and electronics.
EPR measurements showed that rare earth ions occupy mainly cubic sites and
considerably less the axial sites [1].
Laser induced fluorescence spectra reveal expected lines due to Er3+
ions and some extra
lines that could be assign to Ce3+
.
Time-resolved measurements of photoconductivity and photodielectric effect of CeO2:Er
nanoparticles under pulsed laser excitation at 240-540 spectral range were studied by a 8-mm
microwave resonator technique [2] at room temperature. Similar measurement of
microscopic-sized CeO2 powder were performed and compared. Single-photon
photoconductivity spectrum stipulated by band-to-band transitions in 240 – 475 nm spectral
range was observed and the photoconductivity threshold was estimated. Step-wise two-photon
photoionization of Er3+
ions under laser excitation resonant to 4I15/2-
4F3/2,
4F5/2,
4F7/2,
2H11/2
transitions and subsequent transitions to other high-lying states of 4f- configuration situated in
CeO2 conduction band were studied. No any photoconductivity signal was detected. It
testifies low probability of Er3+
ions two-step photoionization and free-charges production.
This work was partially supported by RFBR Foundation grant and Russian Federation
Ministry of Science grant.
[1] M.M. Abraham, R.A. Weeks, G.W. Clark, C.B.Finch, Phys. Rev. 148, 350 (1966)
[2] M.-F. Joubert , S.A. Kazanskii, Y. Guyot, J.-C. Gacon, J.-Y. Rivoire, C. Pedrini, Opt.
Mat., 24, 137 (2003)
101
Fr-4 Electron spin resonance in thin film GdMnO3/SrTiO3
T. P. Gavrilova1)*
, I. V. Yatsyk1)
, R. M. Eremina1)
, D. V. Mamedov2)
, I. I. Fazlizhanov1)
,
A. A. Rodionov2)
, V. I. Chichkov3)
, N. V. Andreev3)
, Ya. M. Mukovskii3)
1) Zavoisky Physical -Technical Institute, Sibirsky tract, 10/7, Kazan, 420029,Russia 2) Kazan (Volga Region) Federal University, Kremlevskaya st. 18, Kazan, 420008 Russia 3) National University of Science and Technology MISiS, Leninskii pr. 4, Moscow, 119049 Russia
*e-mail: [email protected]
We studied the magnetic
properties of GdMnO3 thin films of
thickness about 100 nm deposited
onto the SrTiO3 substrates using the
electron paramagnetic resonance
technique. ESR measurements in thin
film GdMnO3/SrTiO3 were performed
at X-band frequencies. The EPR
spectrum of a GdMnO3 single crystal
consists of only one broad exchange
narrowed line [1], unusual magnetism
is observed at the interface between
the GdMnO3 thin film and substrates
SrTiO3. ESR spectra in
GdMnO3/SrTiO3 in X-band is
presented in fig.1a. As seen from fig.
1a the EPR spectrum of the thin film
GdMnO3/SrTiO3 in X-band consists
from one exchange narrowed line
with g1 ~ 2 and Gd3+
fine structure as
in the case GdMnO3/LaAlO3 [1]. The
angular dependency of the positions
of the fine-structure lines is presented
in fig. 1b.
The temperature dependence
of the ESR spectra in
GdMnO3/SrTiO3 is presented in
fig.1c. With increasing the
temperature from 300К to 340К the
intensity of the fine-structure line
7/2 →5/2 decreases and at 350К
almost disappears. The intensity of
the broad line (H340 Oe) with g~2
increases 3 times in respect to the line
-1/2 →1/2 (H30 Oe) with
increasing the temperature.
[1]. Yatsyk I.V., Mamedov D.V.,
Fazlizhanov I.I., et al. JETP Letters .
96, 416 (2012). Fig. 1. Electron paramagnetic resonance spectrum in thin
film GdMnO3/SrTiO3 in X band at T = 300 K: a) shape
of the spectrum; b) angular dependence;
c) temperature dependence.
1000 2000 3000 4000 5000
430 K
420 K
410 K
400 K
390 K
380 K
370 K
360 K
350 K
340 K330 K
320 K
310 K
H (Oe)
300 K
0 50 100 150 200
1200
1800
2400
3000
3600
4200
AG
ATAUAV ai
aj
akalamar
asat
av
H (
Oe)
angle (deg)
b)
0 2000 4000 6000 8000
H (oe)
a)
102
Fr-5 Localized mechanism of charge trapping around Cr3+
in ZnGa2O4:Cr3+
long-lasting phosphor for in vivo imaging
S. K. Sharma1)
, A. Bessière1)
, D. Gourier1)
, B. Viana1)
, N. Basavaraju2)
, K. R. Priolkar2)
1)LCMCP, Chimie Paristech, 11 rue P. et M. Curie, 75231 Paris Cedex 05, France
2)Department of Physics, Goa University, Taleigao plateau, Goa 403206, India
Long-lasting phosphorescence (LLP) materials with red or near-infrared emission are fast
emerging as probes for in vivo small animal optical imaging after the first demonstration of
the technique in 2007 [1]. In this method, the specially designed LLP nanoparticles, which are
able to circulate in the blood vessels of small animals, are used as luminescent biomarkers.
Making use of red persistent luminescence for optical imaging presents numerous advantages
over conventional fluorescence techniques. The biomarkers are irradiated before injection into
the animal body (ex vivo) making the exposure of animal to high energy radiations
unnecessary. Since the nanoparticles are irradiated outside the animal body and the emission
is in the biological optical window (650 nm to 900 nm), autofluorescence of living tissues is
prevented thus improving the
signal to noise ratio.
ZnGa2O4:Cr3+
has been
discovered to serve this
application with enhanced LLP
properties [2]. It presents
exceptional red LLP when
excited with visible light, i.e.
well below its band gap energy.
The possibility of exciting LLP
within the transparency domain
of living tissues opens
fascinating perspectives for
long-term in vivo imaging of
small animals (tumour
imaging). Thus, understanding
of the LLP mechanism is of
fundamental interest for
biomedical applications. In this work, we present various Thermally Stimulated Luminescence
(TSL) experiments (see figure) obtained by varying heating rates and types of excitation, that
give access to accurate conclusions about the LLP mechanism. The results shows striking
experimental facts pointing to a LLP mechanism entirely localized around CrN2 ions in
ZnGa2O4:Cr3+
. CrN2 ions are Cr3+
ions distorted by an antisite defect as first cationic
neighbour. Such a localized mechanism is unconventional in comparison to the usual band-
assisted LLP mechanisms proposed for the most well-known LLP materials, such as
SrAl2O4:Eu,Dy.
[1] Q. le Masne de Chermontet. al., Proceedings of the National Academy of Sciences, US104
(2007), 9266-9271.
[2] A. Bessière et. al., Optics Express 19 (2011), 10131-10137.
100 200 300 400 500
0
1
2 3 4 5
310
320
330
340
0.0
0.2
0.4
TS
L inte
nsity (
arb
. u.)
Temperature (K)
Excitation energy (eV)
Tm
ain (
K)
3.1 eV = 400 nm
Tl p
eak inte
nsity
103
Fr-6 The sensitization of the intensity of the introcenter 4f -4f luminescence
in crystalline ZnO-films doped with Ce, Yb, Er
E. I. Terukov, M. M. Mezdrogina, M. V. Eremenko, S. N. Smirnov
Ioffe Physical Technical Institute, 194021, Polytehnicheskaya 26, Saint-Petersburg, Russia
ZnO is of great interest for many applications: optoelectronics, photovoltaic, gas
sensors, acoustic optics. ZnO is direct band gap of around 3.4 eV and large exciton binding
energy-60 meV. It can be used for effective luminescence in UV region of spectrum.
The ability to grow ZnO at low temperatures on crystalline silicon substrates gives it
significant potential as a cost effective alternative to nitride materials, which require growth at
high temperatures and also have highly complex epitaxy.
ZnO doped with rare-earth ions (REI) has been investigated extensively as one of opto
electronic material for the design and fabrication light-emitting devices (LED) in visible
(under Tm, Eu, Er doping) and infrared regions of spectrum (under Yb, Er doping).
The purpose of this work is to investigate the influence Ce, Yb (as co-dopants and
activators of emission) and their order of doping on sensitization of the intensity of the intra-
center 4f-4f transitions in Er in crystalline ZnO-films. All ZnO films investigated in this work
by x-ray diffraction analysis were crystalline, prepared by magnetron sputtering ZnO target,
under T=530 ºC, in gas mixture Ar+O. C-Si plates with crystalline SiC thin films (about 20
nm) for minimization of mismatching tension between c-Si and ZnO were used as substrates.
Photoluminescence (PL) spectra all undoped ZnO films (under excitation of He-Cd
laser) are homogeneously broadened with high luminescence intensity I and maximum wave
length λ=368 nm, it corresponds to the position B exciton bounded at neutral donor,
FWHM=37 meV and there is a luminescence band in the long wave range with λMAX=(520-
540) nm.
Laser with λ=532 nm, density of excitation W=4.74·1023
photon·s/cm2
was used for
measurements of intensity intra-center 4f transition Er3+
ions Diffusion method was used in
consequently doping ZnO films with Ce, Yb, Er (ZnO<Ce, Yb, Er). Post-growth process
there was after every impurity doping: Tann=530 ºC, in Ar atmosphere, timeann=1h. In PL
spectra at T=83 K of ZnO<Ce, Yb, Er) films in long-wave region of spectra (1400<λ<1600
nm) there are three lines of luminescence - λ= 1535.8 nm (with greater intensity), λ=1544.8
nm, λ=1548.2 nm, λ=1555.9 nm (with smaller intensity) and with the smallest intensity -
λ=1527.5 и λ=1529 nm lines. It known for intra-center 4f transition for Er
3+ ions is equal to λ=1537.7 nm,
FWHM=3.3 meV and the nearest surrounding Er ion is - C4V as in Si:Er.[1] The influence of
measurements temperature, consequence of doping, concentration of Ce were not observed. It
was observed the consequence of doping Ce, Er, Yb, concentration of Ce influence on PL
spectra in region (900<λ<1200 nm).
The order of doping rare-earth ions ZnO films is not important, because the difference
between values of radius rare-earth ions - rRare very smaller than their difference from rZn and
rO.
It was found for the sensitization of the intensity the luminescence intra-center 4f
transition Er in crystalline ZnO-films doped with Ce, Yb as activators and the order of doping
rare-earth ions ZnO films is not important.
This work was supported by RFFI ( 12-02-00453a, 13-02-00726a).
[1] M.Ishi, Sh.Komuro, T.Morikawa, Yo. Aoyagi, J. Appl. Phys., v.89, N7, 3679 (2001)
104
Fr-7 Magnetotransmission and magnetoreflection of unpolarized light
in magnetic semiconductors
Yu. P. Sukhorukov, N. N. Loshkareva, A. V. Telegin, E. V. Mostovshchikova
Institute of Metal Physics UD of RAS, 620990, S. Kovalevskaya str. 18, Ekaterinburg,
Russia.
E-mail: [email protected]
Optical properties of conventional semiconductors are determined mainly by the effects of
crystal field. Application of magnetic field leads to a weak change in the optical properties of
semiconductors due to the Zeeman splitting of the electron energy levels. In the magnetic
semiconductors effects of the crystal field are comparable to the effects of the exchange
interaction. Applied magnetic field and strong fluctuations of magnetic moments near the
Curie temperature can significantly change the optical properties of magnetic semiconductors.
It leads to the appearance of giant magnetooptical effects such as Faraday and Kerr effects,
magnetotransmission (MT) and magnetoreflection (R) of unpolarized light, as well as to the
changes in the intensity of transmitted and reflected light with the temperature.
We review the optical and magnetooptical properties of magnetic semiconductors such as
Hg(Cd)Cr2Se4 spinels and AxB1-xMnO3 manganites with perovskite structure single crystals,
films and heterostructures (see [1-15] and references therein). We show the R, MT as well
as a change in the intensity of transmitted and reflected light which are a high frequency
response to the magnetoresistance and resistance respectively. Effects can be used to study
process of phase separation (the existence of magnetic and charge inhomogeneities) in
magnetic semiconductors [3-10]. We present also the results of enhancing the R and MT in
manganite thin-films and film structures [4, 14]. The possible applications of the effects are
discussed [6-9, 11-13].
The work is partly supported by the RFBR grants 13-02-00007, 12-02-31505, program
of the Presidium RAS 12-П-2-1034, and grant MK-1048.2012.2.
[1] M. Auslender et al., Sov. Phys. JETP 68(1), 139 (1989).
[2] N.N. Loshkareva, Yu.P. Sukhorukov et al., Fiz. Nizk. Temp. 18(S1), 127 (1992).
[3] E. Gan’shina, N. Loshkareva, Yu. Sukhorukov et al., JMMM 300, 62 (2006).
[4] A.B. Granovskii, Yu.P. Sukhorukov, A.V. Telegin et al., JETP 112(1), 77 (2011).
[5] Yu.P. Sukhorukov, A.V. Telegin, A.B. Granovskii et al., JETP 114(1), 141 (2012).
[6] A. Granovsky, Yu. Sukhorukov, E. Gan’shina, A. Telegin. Magnetorefractive effect in
magnetoresistive materials. In book «Magnetophotonics: From Theory to Applications»,
Springer, Berlin, New-York, 580 Р, (2013).
[7] Yu.P.Sukhorukov, et al., J. Spintronics and Magn. Nanomaterials 1(2), 139 (2012).
[8] Yu.P. Sukhorukov, et al., Patent of RF RU88165, Bull. 30, 27.10.2009.
[9] Yu.P. Sukhorukov, et al., Patent of RF RU2439637, Bull. 1, 10.01.2012.
[10] E.V. Mostovshchikova, N.N. Loshkareva, et al., J. Appl. Phys. 113, 043503 (2013).
[11] N.N. Loshkareva, Yu.P. Sukhorukov, et al., Pisma v Zh. Tekhn. Fiz. 15(17), 83 (1989).
[12] Yu.P. Sukhorukov, N.N. Loshkareva, et al., Tech. Phys. Lett. 29(11), 55 (2003).
[13] Yu.P. Sukhorukov, N.N. Loshkareva, et al., Pisma v Zh. Tekhn. Fiz. 22(1) 85 (1996).
[14] N.N. Loshkareva, Y.P. Sukhorukov, et al., Cryst. Res. Technol. 31, 689 (1996).
[15] Yu.P. Sukhorukov, et al., Phys. Met. and Metallography 107(6), 579 (2009).
105
Fr-8 Divalent cerium and praseodymium ions induced by x-ray irradiation
in fluoride crystals
R. Y. Shendrik1,2)
, E. A. Radzhabov1,2)
, and A. V. Egranov1,2)
1) Vinogradov Institute of geochemistry SB RAS, 664033, Irkutsk, Favorskogo 1a
2) Irkutsk State University, 664003, Irkutsk, Blvd. Gagarina 20
E-mail: [email protected]
First surveys of the optical spectra of divalent rare-earth ions in calcium fluoride were
executed by Feofilov and Kaplyanskii [1]; and McClure and Kiss [2]. However, detailed
investigation of divalent ions induced by x-ray irradiation in CaF2, SrF2, and BaF2 has not yet
been carried out. Study of divalent rare-earth ions in x-ray irradiated fluorides is topically to
understand mechanisms of photochromic centers formation in Ce-doped crystals [3] and
energy transfer mechanism in scintillation process in Pr- and Ce-doped crystals [4, 5].
Crystals of CaF2, SrF2, and BaF2 doped with various concentrations of Ce3+
and Pr3+
ions
were irradiated by x-ray tube with Pd anode at 300 K and 80 K. A Perkin-Elmer Lambda 950
spectrometer was performed to measure absorption spectra in 190-2500 nm spectral region at
10-300 K temperatures. Before x-ray irradiation the absorption spectra of Ce and Pr ions have
the weak sharp line typical of the f -f transitions in infrared (IR) and visible regions of the
spectrum (Fig. 1, curve 1) and strong lines in ultraviolet (UV) region corresponding to
allowed f-d transitions of the trivalent rare-earth ions. After irradiation bands associated with
the dipole-allowed f-d transitions of the divalent ions, extending from the IR or visible to the
UV regions of the spectrum appear (Fig. 1, curve 2). In CaF2 x-ray induced divalent Pr and Ce
ions are stable at 300 K.
Fig. 1. Optical absorption spectra of CaF2-0.1 mol. % Pr
3+ at 300 K before (curve 1) and
after (curve 2) x-ray irradiation.
In this work, we discuss a role of divalent rare-earth ions in processes of energy transfer
and PC centers formation.
[1] A. A. Kaplyanskii and P. P. Feofilov, Opt. i Spektr.,13, 235 (1962).
[2] D. S. McClure and Z. J., J. Kiss, Chem. Phys. 39, 3251 (1963).
[3] A. V. Egranov, T. Yu. Sizova, Journal of Physics and Chemistry of Solids, 74, p. 530-534
(2013)
[4] R. Shendrik, E. Radzhabov, IEEE TNS, 59, pp. 2089 – 2094 (2012)
[5] R. Shendrik, E.A. Radzhabov, A.I. Nepomnyashchikh, Radiation Measurements (2013),
http://dx.doi.org/10.1016/j.radmeas.2013.01.054
106
Fr-9 Ab Initio Study of Structural and Vibrational Properties of Y2CaGe4O12
Optical Host
I. I. Leonidov1)
, V. P. Petrov2)
, V. A. Chernyshev2)
, A. E. Nikiforov2)
,
E. G. Vovkotrub3)
, A. P. Tyutyunnik1)
, V. G. Zubkov1)
1)
Institute of Solid State Chemistry, UB RAS, 620990, Ekaterinburg, Russia 2)
Ural Federal University, 620002, Ekaterinburg, Russia 3)
Institute of High-Temperature Electrochemistry, UB RAS, 620990, Ekaterinburg, Russia
E-mail: [email protected]
Lanthanide-doped germanates have been widely studied in various fields of luminescence
spectroscopy and materials science [1–4]. Germanates attract much attention as promising
host matrices for light emitting devices, scintillators and phosphors. The germanate-based
materials usually demonstrate high chemical, mechanical and thermal stability [5].
Upconversion luminescence in Y2CaGe4O12:Er3+
, Yb3+
under a 980 nm laser excitation, as
well as eye-safe laser performance at 1540 nm, has been shown in our previous paper [6]. The
present report is focused on vibrational spectroscopic studies and DFT calculations of this
optical host.
Structural and vibrational features of the Y2CaGe4O12 cyclotetragermanate have been
computed ab initio within a periodic approach using the CRYSTAL09 program package and
six DFT functionals with all-electron Gaussian-type basis sets. The selected compound, for
which the accurate experimental data are available, has been used as a representative of a
large germanate family Ln2MGe4O12, Ln = lanthanide, Y; M = Ca, Mn, Zn. Experimental
lattice parameters and internal coordinates have been optimized. FTIR and Raman spectra of
the powder sample have been measured. The full harmonic vibrational spectra of Y2CaGe4O12
computed at the Γ point have been compared well with the experimental IR and Raman data,
the factor group analysis of the possible crystal lattice vibrations has been employed. The
number of the observed vibrational modes in the spectra is consistent with computational data
and the results of the factor group analysis. The calculated values of wavenumbers are more
accurate when computed with hybrid functionals, with the best performance provided by
B3LYP and recently established WC1LYP. A new structural model for Y2CaGe4O12 implied
a tetragonal-to-orthorhombic symmetry reduction has been proposed according to the results
of computational procedures. The set of computed harmonic frequencies has not shown any
negative frequency that characterizes the orthorhombic phase (S.G. Cmme) as a minimum.
This work was supported by UB RAS under grants Nos. 12–P–3–1003, 12–T–3–1009, and
13–3–NP–686.
[1] S.E. Sarkisov, A.A. Kaminskii, A.V. Butashin, Yu.E. Perlin, V.N. Enakii, M.G. Blazha,
Phys. Status Solidi A 119 (1990) 607–619.
[2] D. Jaque, J.G. Sole, Phys. Rev. B 70 (2004) 155116.
[3] A. Witkowska, B. Padlyak, J. Rybicki, J. Non-Cryst. Solids 352 (2006) 4346–4350.
[4] D. Uhlich, J. Plewa, Th. Jüstel, J. Lumin. 128 (2008) 1649–1654.
[5] E.L. Belokoneva, Russ. Chem. Rev. 63 (1994) 559–576.
[6] I.I. Leonidov, V.G. Zubkov, A.P. Tyutyunnik, N.V. Tarakina, L.L. Surat,
O.V. Koryakova, E.G. Vovkotrub, J. Alloys Compd. 509 (2011) 1339–1346.
107
min 2
2 min1
0( ) ( ) 1 cos( ( )) / 2, ( ) ( ') ', 2 ( ') ',
tt
t t
I t I t t t Z t dt Z t dt
Fr-10 Modulation of an echo shape by a pulsed perturbation
as a new spectroscopy method
V. N. Lisin, A. M. Shegeda
Zavoisky Physical Technical Institute of RAS, 420029 Kazan, Russia
E-mail: [email protected]; [email protected]
We report about a new spectroscopy method involving a change in the time shape of the
echo pulse in the presence of a perturbation, which splits the frequencies of the transitions of
two or more ion subgroups of the echo active ions. In the case of two ion subgroups an
expression for the intensity of two pulse echo can be written as
if a perturbation is switched on after the second pulse of echo excitation. Here I0(t) is echo
intensity without perturbation, Z(t) and φ(t) are the frequency splitting (in rad/sec) and
accordingly the relative phase (in rad) between two ion subgroups due to external
perturbation. If a pulsed perturbation is applied at the moment of the appearance of the echo
signal then the time shape of the echo signal is changed. Moreover, the echo time shape can
have oscillating character. A dip (a minimum) should be observed in the echo signal when
φ(tmin1) = π and the next dip when φ(tmin2) = 3π. The distance between the dips on the time
scale may be used to determine the frequency splitting and the spectroscopy parameters of
excited state of echo ions. The frequency splitting can be much less than inhomogeneous
linewidth. The method can be applied at excitation of an echo in any range of wavelengths.
In our work, we apply the method to the optical systems in which Zeeman effect is
manifested. Some results and experimental setup may be found in [1, 2]. The transition
frequencies of ions are switched by weak pulsed magnetic field H(t) acting during the time of
the photon echo pulse and directed along the crystal c-axis: Z(t') = β(ge|| gg||)H(t')/ħ .
The modulation of the photon echo signal shape was observed in LuLiF4:Er3+
(see
Fig.) and YLiF4:Er3+
for -polarization. The studied transition is 4I15/2 –>
4F9/2. Using the time
interval between the two nearest minima, we determined the difference between the g-factors
of the ground 4I15/2 (gg||) and excited
4F9/2 (ge||) states of the Er
3+ ion in LuLiF4 for the known
amplitude of the pulsed magnetic field: gg|| = 3.09 → ge|| = 10.27.
[1] V. N. Lisin, A. M. Shegeda, and K. I. Gerasimov, JETP Lett. 95, 61 (2012)
[2] V. N. Lisin, A. M. Shegeda, JETP Lett. 96, 298 (2012)
0 10 20 30 40 50 60 70 80
0,0
0,4
0,8
1,2
1,6
0 10 20 30 40 50 60 70 80
echo without magnetic pulse
magnetic pulse
Ech
o i
nte
nsi
ty (
arb
. u
nit
s) LuLiF4:Er
3+
echo with magnetic pulse
Time (ns)
8,5 ns
Zeeman splitting
Z=1/8,5 ns = 117 MHz
108
Poster session I
109
PI_1 Effects of non-linear vibronic interaction on orbital and magnetic structures of
BiMnO3
L.E. Gonchar1,2)
, A.E. Nikiforov2)
1)
Ural State University of Railway Transport, 620034, 66, Kolmogorov St., Ekaterinburg, Russia 2)
Ural Federal University, 620002, 19, Mira St., Ekaterinburg, Russia
BiMnO3 crystal is discussed now as a possible multiferroic crystal [1]. The complicated
crystal structure, orbital ordering and frustrated magnetic structure are interrelated with each
other because of cooperative Jahn-Teller effect.
Being perovskite manganite crystal, BiMnO3 differs markedly from rare-earth manganites by
the crystal structure (monoclinic versus orthorhombic one), by the orbital structure, and by
magnetic structure (frustrated ferromagnet versus A-type antiferromagnet). This is a reason of
insufficiency of the model of linear vibronic interaction [2] successfully used for description
of rare-earth manganites. In order to take into account a strong distortion of the crystal
structure and it's effect on the orbital structure, the extended model of vibronic interaction is
supposed:
vib lin QQ RH H H H , (1)
where Hlin is linear nearest-neighbor Jahn-Teller interaction operator, build in eigenfunction
of 5E ground state of 3d Mn
3+ ion, HQQ is anharmonic nearest-neighbor Jahn-Teller interaction
operator, and HR is linear next nearest-neighbor Jahn-Teller interaction operator, depending
upon symmetrized eg- and t1g distortions of oxygen and bismuth coordination. The possible
ranges of vibronic interactions parameters values are predicted.
The magnetic structure is described in the model of orbitally-dependent superexchange
interaction [3].
This model allows to describe the magnetic properties of BiMnO3. Taking into account
additional terms of vibronic Hamiltonian plays the crucial role for description of magnetically
frustrated compounds, because the slight change of orbital structure move the equilibrum
magnetic structure to the other type.
[1] T. Kimura, S. Kawamoto, I. Yamada, M. Azuma, M. Takano, Y. Tokura, Phys. Rev B 67,
180401R (2003); I. V. Solovyev, and Z. V. Pchelkina, Phys. Rev B 82, 094425 (2010)
[2] L.E. Gonchar, T.O. Nikitina, A.E. Nikiforov, JETP, 116, 812 (2013)
[3] L. E. Gontchar, A. E. Nikiforov, Phys. Rev B 66, 014437 (2002)
110
PI_2 Electronic structure and origin of luminescence in Bi-containing phosphates
and molybdates
Yu. Hizhnyi1)
, S. Nedilko1)
, V. Chornii1)
, T. Nikolaenko
1),
M. Slobodyanik1)
, K. Terebilenko1)
, V. Boyko2)
, V. Sheludko3)
1)
Taras Shevchenko National University of Kyiv, 64 Volodymyrska st., 01601 Kyiv, Ukraine 2)
National University of Life and Environmental Sciences of Ukraine, 5 Geroiv Oborony st.,
03041 Kyiv, Ukraine 3)
Oleksandr Dovzhenko Hlukhiv National Pedagogical University, 24 Kyjevo-Moscovs’ka
St., 41400 Glukhiv, Ukraine
The alkali metal and bismuth phosphates/molybdates have attracted much attention
last decade due to their practical applications as effective components for white light emission
diodes and laser materials [1, 2]. Due to close ionic radii, the Bi3+
cations can be easily
substituted by the luminescent RE3+
ions. While the luminescence properties of the RE-doped
Bi-containing oxide compounds were studied intensively, less efforts were spent for studying
of their fundamental physical properties, namely the electronic structure, origin of intrinsic
luminescence and mechanisms of excitation energy transfer. However clarification of these
issues is an indispensable condition for elaboration of effective luminophores on the base of
the RE-doped crystals. In this work we apply the luminescent and optical spectroscopy studies
under various types of excitations together with electronic structures calculations for pure and
RE-doped Bi-containing compounds in order to establish the origin of intrinsic emission
centers in mentioned compounds.
The polycrystalline samples of undoped and RE-doped BiPO4, K3Bi5(PO4)6,
K2Bi(PO4)(MoO4), K2Bi(PO4)(WO4) and K5Bi(MoO4)4 (RE = Eu, Tb, Pr, Tm, Ce) crystals
were synthesized by spontaneous crystallization method. The PL emission and excitation
spectra were measured under excitation with synchrotron radiation (4 – 25 eV) at
SUPERLUMI station at HASYLAB (DESY), Hamburg, Germany. Dependencies of
luminescence intensity and decay time on temperature were also obtained under N2-laser
excitation (λexc =337.1nm) in 4.2 – 300 K temperature region. Diffuse reflectance spectra of
fine-grained powdered samples were measured at 300 K using double-beam
spectrophotometer. Absorbance spectra were calculated from the diffuse reflectance using the
Kubelka-Munk relation. The electronic structures of the perfect crystals were calculated by
the FLAPW method realized in Wien2k program package [3].
The PL emission spectra of all undoped compounds obtained under synchrotron
excitation are characterized by complex emission bands in 400-850 nm spectral region.
Calculated partial densities of states indicate that the Bi cations, as well as MoO4 groups in
the molybdate hosts, play a dominant role of in the processes of luminescence excitation.
Analysis of diffuse reflectance and luminescence excitation spectra allows estimation of the
energy gap (Eg) parameters of the studied compounds. Temperature dependencies of decay
time constants and emission intensity show that “blue-violet” emission components have the
Bi3+
-related origin whereas emission components of the molybdate crystals in the red spectral
region are related to transitions in MoO4 groups.
[1] X. Hea, M. Guan, N. Lian, J., et al. J. Alloys Compd. 181, 2828-2836 (2008)
[2] T. Kim and Sh. Kang. J. Lumin. 122-123, 964-966 (2007)
[3] P. Blaha, K. Schwarz, G. Madsen, et al, 2001. ISBN 3-9501031-1-2.
111
PI_3 Electronic structure and origin of luminescence of undoped and RE-doped
PbMoO4 and Pb2MoO5 crystals
V. Chornii1)
, S. Nedilko1)
, Yu. Hizhnyi1)
, M. Trubitsyn
2), I. Volnyanskaya
2)
1) Taras Shevchenko National University of Kyiv, 64 Volodymyrska st., 01601 Kyiv, Ukraine
2) Oles Honchar Dnipropetrovsk National University, Naukova Street 9, 49050,
Dnipropetrovsk, Ukraine
E-mail: [email protected]
The photoluminescence (PL) and scintillation properties of the PbMoO4 crystals have
been intensively studied during the last decade due to their applications as scintillating and
acousto-optic materials. The electronic structure of perfect and defect-containing PbMoO4
crystals was the subject of several theoretical works. However, few important issues,
including the origin of the violet emission band (peak position near 400 nm) observed at some
conditions in PbMoO4, as well as role of the lead cations in the luminescence processes are
still the subject of discussion. The PL properties of the lead oxymolybdate crystals Pb2MoO5
have attracted much lesser attention. At present, available literature data on the PL emission,
PL excitation and decay kinetics of undoped lead oxymolybdates is not enough for
understanding an origin of luminescence centers in Pb2MoO5. No data concerning electronic
structure of Pb2MoO5 crystal could be found in literature at the present moment. The PbMoO4
and Pb2MoO5 hosts have different coordination of Pb cationic positions. The MoO4
oxyanionic groups have a form of regular (for PbMoO4) or slightly distorted (for Pb2MoO5)
tetrahedrons. These interesting features can in some way be manifested in the PL
spectroscopy and the electronic structure data, and can help to solve the problems related to
PL properties of the lead molybdate.
The set of undoped and doped with Cu2+
, Yb3+
, Nd3+
and Gd3+
ions PbMoO4 and Pb2MoO5
single-crystalline samples was grown by Czhochralskii technique with stoichiometric
composition of initial components as well as with excess of MoO3 oxide in initial batch. The
VUV-excited luminescence was studied on SUPERLUMI station at HASYLAB (DESY),
Hamburg, Germany in 3.7 – 14 eV region of excitation energies at T = 8 K.
Electronic structures, optical constants and dielectric permittivities curves (ε1, ε2) of perfect
PbMoO4 and Pb2MoO5 were calculated by the FLAPW method realized in Wien2k program
package. The optical characteristics of both compounds are compared with obtained
experimental data. Electronic structure of the perfect Pb2MoO5 crystal was calculated at the
first time.
Calculated partial densities of states indicate that the MoO4 groups play a dominant role of in
the processes of photoluminescence excitation in the PbMoO4 and Pb2MoO5 crystals.
Intrinsic PL spectra of investigated PbMoO4 and Pb2MoO5 crystals obtained under
synchrotron excitation are characterized by complex emission bands in 400-750 nm spectral
region. Relation between intrinsic and impure luminescence of investigated crystals is
analyzed.
Origin of the PL emission and excitation bands in PbMoO4 and Pb2MoO5 single crystals as
well as the role of the molybdate anions, lead cations and impurity ions in the luminescence
processes is revealed in comparative analysis of experimental spectra and calculation results.
112
PI_4 Influence of f-f electron transitions on the local properties in vicinity of the excited
ions in trigonal Alumo- and Ferroborates
A.V. Malakhovskii1)
, S.L.Gnatchenko2)
, I.S.Kachur2)
, V.G.Piryatinskaya2)
,
A.L. Sukhachev1)
, A.E. Sokolov1)
, V.L.Temerov1)
, I.A. Gudim1)
1)
L.V. Kirensky Institute of Physics, Siberian Branch of Russian Academy of Sciences ,
660036 Krasnoyarsk, Russia 2)
B.Verkin Institute for Low Temperature Physics and Engineering, National Academy of
Sciences of Ukraine, 61103 Kharkov, Ukraine
E-mail:[email protected]
Crystal and magnetic structure directly depend on electronic structure of atoms composing
the crystal. Electronically excited atom is, actually, impurity atom, and, consequently, the
local properties of the excited atom environment can change. These local changes, in turn, can
change properties of electronic states and electron transitions. Spectroscopic manifestation of
such local distortions was first observed in Ref. [1]. Present work is devoted to study of the
similar phenomenon in crystals of the type R(Al,Fe)3(BO3)4, where R is the rare earth ion,
when f-f transitions take place. These transitions are allowed only due to odd distortions of the
environment. Therefore, their properties are the sensitive tool for detection of the distortions.
There were observed few experimental results, which testify to the phenomenon under
discussion: 1) Abrupt change or another singularities of some spectroscopic characteristics of
f-f transitions at temperature, when there are no corresponding changes in the ground state
(TbFe3(BO3)4 [2]). 2) Different
temperature dependences of intensities
of the same f-f transition in π and σ
polarizations and (or) deviation of these
dependences from those followed only
from the thermal population of the
ground state crystal field splitting
sublevels (TmAl3(BO3)4 and
YbAl3(BO3)4 [3]). 3) Larger number of
observed absorption lines than that
followed from the local symmetry of
the 4f ion position in the ground state
(TmAl3(BO3)4 [4]). 4) Violation of the
local symmetry depends not only on the
excited, but also on the initial state
(DyFe3(BO3)4). 5) Exchange splitting of the excited state appears at lower temperature than
that of the ground state. Fig. 1 demonstrates the splitting of one of the absorption lines of Nd3+
ion in Nd0.5Gd0.5Fe3(BO3)4 due to the exchange splitting of the excited state. 6) Orientation of
magnetic moments changes in the excited state (revealed in Nd0.5Gd0.5Fe3(BO3)4).
[1] W.W. Holloway, E.W. Prohovsky, M. Kestigian, Phys. Rev. 139 (1965) A954.
[2] A.V. Malakhovskii, S.L. Gnatchenko, I.S. Kachur, V.G. Piryatinskaya, A.L. Sukhachev,
V.L. Temerov, Eur. Phys. J. B 80 (2011) 1.
[3] A.V. Malakhovskii, A.L. Sukhachev, S.L. Gnatchenko, I.S. Kachur, V.G. Piryatinskaya,
V.L. Temerov, A.S. Krylov, I.S. Edelman. J. Alloys Comp. 476 (2009) 64-69.
[4] A.V. Malakhovskii, I.S. Edelman, A.E. Sokolov, V.L. Temerov, S.L. Gnatchenko, I.S.
Kachur, V.G. Piryatinskaya, J. Alloys Comp. 459 (2008) 87.
0 5 10 15 20 25 30 3516920
16921
16922
16923
16924
16925
-polarization
E (
cm
-1)
T ( K )
-polarization
TN
Fig. 1
113
PI_5 Magneto-optical activity of f-f transitions in trigonal Alumo- and Ferroborates
A. L. Sukhachev, A.V. Malakhovskii, T.V. Kutsak, A.Yu. Strokova, A.E. Sokolov,
V.L. Temerov, I.A. Gudim
L.V. Kirensky Institute of Physics, Siberian Branch of Russian Academy of Sciences, 660036
Krasnoyarsk, Russia.
E-mail: [email protected]
There are two aspects in the studying of magnetic circular dichroism (MCD) of f-f
transitions: 1) nature and properties of MCD itself and 2) MCD as a source of information
about properties of electron transitions and electronic states. Both of these aspects are
considered in the present communication in application to some rare earth containing crystals
of hantite structure: DyFe3(BO3)4, Nd0.5Gd0.5Fe3(BO3)4, ErAl3(BO3)4, TmAl3(BO3)4,
YbAl3(BO3)4.
Magnetic circular dichroism and polarized optical absorption spectra of the enumerated
crystals were measured. From these measurements, temperature dependences of the
paramagnetic magneto-optical activity (MOA) of the electric dipole forbidden f-f transitions
were obtained. It was revealed that, in contrast to allowed transitions, temperature
dependences of the MOA of some f-f transitions substantially deviate from the Curie-Weiss
law (see, e. g. Fig. 1 for ErAl3(BO3)4). Value “C” in Fig. 1 is the dimensionless parameter in
formula c=CμBH/k(T-θ) for MOA, which should be constant if the Curie-Weiss law is valid.
Comparison of the experimental results
with the theory of f-f transitions MOA [1]
has shown that: 1) maximum MOA of f-f
transitions is the same as that of allowed
transitions, 2) the MOA of f-f transitions
can consist of several contributions of
different values and signs, 3) ratio of the
contributions is determined by the
symmetry of the crystal field, 4) the ratio
of the contributions depends on population
of components of the ground state crystal
field splitting, that results in deviation of
the MOA temperature dependence from
the Curie-Weiss law.
The studied crystals have trigonal symmetry. Therefore, in a first approximation 4f wave
functions can be described by JMJ , states. Splitting of the states in magnetic field are
proportional to MJ, but selection rules are governed by the crystal quantum number μ which
has for states with the half integer moment in trigonal symmetry three values: +1/2, -1/2, 3/2
(±3/2). Between values MJ and μ there is the following correspondence:
MJ = ±1/2, ±3/2, ±5/2, ±7/2, ±9/2, ±11/2, ±13/2, ±15/2
μ = ±1/2, (±3/2), 1/2, ±1/2, (±3/2), 1/2, ±1/2, (±3/2)
Selection rules for μ are the same as for magnetic quantum number m in a free atom. From the
MCD spectra, the Zeeman splitting of absorption lines were found. Comparison of the
experimental MCD spectra with the theoretical predictions permitted to find not only
symmetry of states but also their origin from states of the type JMJ , .
[1] A.V. Malakhovskii, V.A. Isachenko, A.L. Sukhachev, A.M. Potseluyko, V.N. Zabluda,
T.V. Zarubina, I.S. Edelman, Physics of the Solid State 49, 701 (2007).
114
PI_6 Spin-phonon and electron-phonon interactions in multiferroic RFe3(BO3)4 probed
by terahertz spectroscopy
K.N. Boldyrev1)
, M.N. Popova1)
, T.N. Stanislavchuk2)
, A. Sirenko2)
, L.N. Bezmaternykh3)
1)
Institute of Spectroscopy, Russian Academy of Sciences, 142190, Troitsk, Moscow, Russia 2)
Department of Physics, New Jersey Institute of Technology, 07102, Newark, NJ, USA 3)
Kirenskii Institute of Physics, Siberian Branch of RAS, 660036, Krasnoyarsk, Russia
Rare earth iron borates with the general formula RFe3(BO3)4 (R = Y, La-Lu) crystallize in
trigonal non-centrosymmetric structure, SG R32. Iron borates with the radius of the R3+
ion
greater than that of Sm3+
undergo a structural phase transition into also trigonal but less
symmetric P3121 low-temperature phase. All these crystals order antiferromagnetically at
temperatures of about 40 K, demonstrate the magneto(di)electric effects, and belong to a new
class of multiferroics [1].
The present work concerns the study of EuFe3(BO3)4 that undergoes the R32 → P3121 phase
transition at TS = 58 K (which is the lowest observed Ts among RFe3(BO3)4) and of iron
borates that have no structural phase transition, namely, of PrFe3(BO3)4, NdFe3(BO3)4, and
SmFe3(BO3)4. We study transmission, reflection, and ellipsometry spectra in the terahertz
region (0.6 – 6.0 THz or 20 – 200 cm-1
) in a wide temperature range (4 – 350 K). The phonon
frequencies of EuFe3(BO3)4 demonstrate pronounced changes at TS, consistent with the
observed peculiarities in the dielectric constant and thermal expansion [1]. Smaller, but
clearly visible phonon shifts were registered below TN [2]. Similar peculiarities at TN were
observed also in the spectra of
other studied iron borates, thus
evidencing spin-phonon coupling
in these multiferroic compounds.
We suggest a mechanism of such
coupling in EuFe3(BO3)4, based
on our experimental data [2]. In
addition, praseodymium and
neodymium iron borates
demonstrate an interaction
between electronic levels of the
rare earth and the lattice
phonons. This interaction is the
most pronounced for
PrFe3(BO3)4 where an almost
precise resonance between the
frequencies of electronic and lattice excitations exists (see Fig.1).
This work was supported by the Russian Foundation for Basic Research (grant 12-02-
31028) and the grant of the President of the Russian Federation (MK - 1700.2013.2).
[1] A.M. Kadomtseva, Yu.F. Popov, G.P. Vorob’ev et.al., J. Low Temp. Phys. 36, 640 (2010)
[2] K.N. Boldyrev, T.N. Stanislavchuk, S.A. Klimin, M.N. Popova, L.N. Bezmaternykh,
Phys. Lett. A. 376, 2562 (2012)
115
PI_7 Low temperature behavior of f-f transitions in Nd0.5Gd0.5Fe3(BO3)4
multiferroic crystal
S.L. Gnatchenko1)
, I.S. Kachur1)
, V.G. Piryatinskaya1)
, A.V. Malakhovskii2)
, A.L.
Sukhachev2)
, I.A. Gudim2)
1)
B.Verkin Institute for Low Temperature Physics and Engineering, National Academy of
Sciences of Ukraine, 61103 Kharkov, Ukraine 2)
L.V. Kirensky Institute of Physics, Siberian Branch of Russian Academy of Sciences,
660036 Krasnoyarsk, Russia
E-mail: [email protected]
Two-component rare-earth ferroborate Nd0.5Gd0.5Fe3(BO3)4, as well as the pure Nd- and
Gd-ferroborates, possesses multiferroic properties. In this crystal antiferromagnetic easy plane
ordering occurs at TN = 32 K and remains down to 2 K [1]. At temperatures T < 11 K
hysteresis in magnetization in the easy plane was found that indicated an appearance of static
magnetic domains [1]. In the field range 1 – 3.5 kOe displacement of domain walls and spin-
flop transition take place.
The present work is devoted to study of optical absorption spectra of Nd0.5Gd0.5Fe3(BO3)4 in
the temperature region of magnetic ordering and in external magnetic fields. Analysis of the
absorption and magnetic circular dichroism spectra allowed us to identify components of the
crystal field splitting of electronic states.
0 5 10 15 20 25 30 35
17055
17060
17065
17070
E (
cm
-1)
T ( K )
TN
0 5 10 15 20 25 3016920
16922
16924
16926
H C3
E (
cm
-1)
H (kOe)
Fig. 1. Temperature dependences of line positions in Fig. 2. Positions of absorption lines as functions
the region of optical transition 4I9/2 2G7/2 + 4G5/2. of external magnetic field strength. H C3.
At temperatures lower than TN the splitting of the ground and excited Kramers doublets of
Nd3+
in the exchange field of the Fe-subsystem occurs. Fig. 1 demonstrates the splitting of
one of the absorption lines (optical transition 4I9/2
2G7/2 +
4G5/2) as a result of the exchange
field effect.
The absorption spectra of Nd0.5Gd0.5Fe3(BO3)4 were studied in external magnetic fields
applied both along and perpendicular to C3-axis at T = 2 K. In the region of the spin-flop
transition at H C3 abrupt changes in energy position, intensity and width of lines are
observed (e.g., Fig. 2). The changes in absorption spectra at H < 3.5 kOe demonstrate
hysteresis, that corresponds to the hysteresis in magnetization.
[1] A.V. Malakhovskii, E.V. Eremin, D.A. Velikanov, A.V. Kartashev, A.D. Vasil’ev, I.A.
Gudim, Fiz. Tverd. Tela 53 (2011) 1929 [Phys. Solid State 53 (2011) 2032].
116
PI_8 Modeling of the non-adiabatic effect in the 4f1 – 5d
1 absorption spectrum
in the LiYF4:Ce3+
crystal
R.Yu. Yunusov, O.V. Solovyev
Kazan Federal University, Kremlevskaya 18, 420008 Kazan, Russia
Introduction. In the measured 4f1 – 5d
1 absorption spectrum of the LiYF4:Ce
3+ crystal the
maxima of the bands corresponding to transitions between the ground state and the third and
fourth 5d1 levels (the components of the orbital doublet) of the Ce
3+ ions are split for
approximately 1900 cm-1
[1]. Such a large splitting cannot be explained by varying the
parameters of the impurity Ce3+
ion Hamiltonian, as it was shown in [1]. It was suggested in
[2] that this splitting should be ascribed to the Jahn-Teller effect. Nowadays there is no
satisfactory theory that allows calculating the shape of an optical spectrum taking into account
the non-adiabatic part of interaction of an optical center with the lattice vibrations, but the
moments of such spectrum can be calculated exactly [3]. In this work we calculated the first
few moments of the LiYF4:Ce3+
absorption spectrum and showed that the mentioned above
large splitting of the electron-vibrational band can be explained by taking into account the
non-adiabatic electron-phonon interaction.
Moments of the «non-degenerate level – two degenerate levels» transition. The model
Hamiltonian contains the energy of optical electrons of the impurity ion (including interaction
with the static crystal field), the energy of the vibrational subsystem in the harmonic
approximation, and the electron-phonon interaction linear in the normal coordinates. Zero
temperature case was considered. To take into account mixing of the 5d1 levels of the Ce
3+ ion
by non-adiabatic interaction with phonons, we derived calculating formulas for the second,
third and fourth centered moments for a transition between a non-degenerate level and two
degenerate levels utilizing the Green’s functions of the vibrational subsystem.
Modeling of the non-adiabatic effect in the 4f1 – 5d
1 absorption spectrum. Details of the
modeling of the absorption spectrum in LiYF4:Ce3+
crystal in the adiabatic approximation can
be found in [2,4]. No parameters of the model were additionally fitted in this work. The
calculated values of the second, third and fourth centered non-adiabatic moments of
absorption bands corresponding to transitions from the ground state to the third and fourth 5d1
levels of the Ce3+
ion are an order of magnitude greater than the corresponding moments in
the adiabatic approximation. The non-adiabatic shape of the absorption spectrum in
LiYF4:Ce3+
crystal was calculated with the use of the obtained non-adiabatic moments and
Gram-Sharlier series with the Gaussian curves as test distributions (the use of Gaussian
curves is justified since the corresponding experimental bands also have Gaussian shape). The
maxima of the third and fourth bands in the calculated absorption spectrum are split for
approximately 2000 cm-1
. This is in good agreement with experimental data.
Conclusions. We showed that the splitting between the maxima of the third and fourth bands
in the 4f1 – 5d
1 absorption spectrum of the LiYF4:Ce
3+ crystal is mainly caused by the non-
adiabatic interaction of the 5d electron with crystal lattice vibrations.
Acknowledgements. This work was supported by the RFBR Grant 12-02-31606.
[1] M.F. Reid et al. Phys. Rev. B 62, 14744 (2000).
[2] B.Z. Malkin et al. J. Lumin. 125, 175 (2007).
[3] Yu.E. Perlin, B.S. Tsukerblat, Effects of Electronic–Vibrational Interaction in the Optical
Spectra of Impurity Paramagnetic Ions, Kishinev: Shtiintsa, 1974.
[4] O.V. Solovyev, B.Z. Malkin, J. Mol. Struct. 838, 176 (2007).
117
PI_9 Modeling of quadratic non-Condon effect in the 4f14
– 4f13
5d
optical spectra in the LiYF4:Lu3+
crystal
O.V. Solovyev, R.Yu. Yunusov
Kazan Federal University, Kremlevskaya 18, 420008 Kazan, Russia
In the present work we model absorption and luminescence spectra in the LiYF4:Lu3+
crystal
corresponding to symmetry forbidden 4f14
– 4f13
5d transitions in the Lu3+
ion at zero
temperature taking into account the quadratic non-Condon effect. This effect has not been
modeled earlier in literature. The statement of the problem is determined by necessity of
interpreting the interconfigurational 4fn – 4f
n-15d optical spectra of impurity heavy rare-earth
ions (n > 7) for which transitions between the ground state of the 4fn electronic configuration
and the lowest-energy state of the 4fn-1
5d electronic configuration are spin- or symmetry
forbidden and the Condon approximation is violated.
In [1] we derived analytical expressions for the absorption and luminescence form-functions
of impurity ions at zero temperature in the adiabatic approximation taking into account the
quadratic non-Condon effect. In the present work we apply the developed theory to simulation
and analysis of the non-Condon spectra of the LiYF4:Lu3+
crystal in the range of symmetry
forbidden transitions between the two lower electronic states of the excited Lu3+
ion
configuration 4f13
5d and the 4f14
ground state.
To simulate spectral envelopes of the LiYF4:Lu3+
crystal we use the microscopic model of
electron-phonon interaction derived in [2, 3]. Simulation involves calculations of crystal field
parameters for a 5d electron as explicit functions of lattice ion’s coordinates in the framework
of the exchange charge model, numerical diagonalization of the effective impurity ion
Hamiltonian containing energies of electrostatic Coulomb and exchange interactions between
electrons, spin-orbit interactions and the crystal field interactions for the ground (4f14
) and
excited (4f13
5d) electronic configurations, calculations of the 5d-electron-phonon coupling
constants, and simulations of the band shapes by making use of the realistic phonon spectrum
of the host LiYF4 lattice. Parameters of the model have been established in [2] by fitting the
measured excitation spectra of the LiYF4:Lu3+
crystal corresponding to the allowed 4f14
–
4f13
5d transitions in the Lu3+
ion. No parameters are additionally fitted in the present work.
The calculated quadratic non-Condon contribution (including the interference between linear
and quadratic non-Condon effects) to the LiYF4:Lu3+
crystal spectra in the considered range
of energies is stronger than the linear non-Condon contribution, with the ratio of integral
intensities of these contributions close to 4. The absence of zero-phonon lines in the measured
excitation and luminescence spectra of the LiYF4:Lu3+
crystal [2] is discussed on the basis of
group-theoretical analysis of analytical expressions for the quadratic non-Condon form-
functions of absorption and luminescence.
The results obtained can be used in further investigation of mechanisms of optical spectra
formation in the case of the Condon approximation violation, in modeling and interpretation
of interconfigurational 4fn – 4f
n-15d absorption and luminescence spectra of impurity rare
earth ions, which is necessary for predicting characteristics of potential phosphors and
scintillators in the vacuum ultraviolet region of the spectrum of electromagnetic radiation.
This work was supported by the RFBR Grant 12-02-31606.
[1] R.Yu. Yunusov, O.V. Solovyev, J. Phys.: Conf. Ser. 324, 012035 (2011).
[2] M. Kirm et al. Phys. Rev. B. 75, 075111 (2007).
[3] O.V. Solovyev, B.Z. Malkin, J. Mol. Struct. 838, 176 (2007).
118
PI_10 Testing downconversion effect in KGd2F7 doped with Tb3+
V.N. Makhov1)
, N.M. Khaidukov2)
1)P. N. Lebedev Physical Institute, 119991, 53 Leninskii Prospekt, Moscow, Russia
2)N. S. Kurnakov Institute of General and Inorganic Chemistry, 119991, 31 Leninskii
Prospekt, Moscow, Russia
E-mail: [email protected]
In recent years the mechanism of quantum cutting through downconversion has been
proposed for obtaining the high-efficiency VUV-excited phosphors to be used in mercury-free
fluorescent lamps [1, 2]. In such phosphors the absorption of one VUV quantum results in
irradiation of two photons in the visible range of spectrum due to energy transfer between
different ions. In particular, the quantum cutting effect was proposed to occur in phosphors
containing a pair of ions Gd3+
-Tb3+
[3, 4]. The realization of downconversion in this ion
combination requires the efficient energy transfer from Tb3+
to Gd3+
owing to cross-relaxation
from high-lying (non-relaxed) 4f5d levels of Tb3+
. However, the efficiency of this mechanism
remains unclear, as there is the possibility of fast non-radiative relaxation from high-lying
4f5d levels to lower-lying 4f5d and 4f levels of Tb3+
. In the present work the possible
downconversion effect has been tested in KGd2F7 crystals doped with Tb3+
in various
concentrations (from 0.5 to 40 at. %).
The measurements of emission (300-700 nm) and excitation (50-300 nm) spectra were
performed using synchrotron radiation for excitation. The crystals were synthesized under
hydrothermal conditions. In order to estimate the efficiency of possible quantum cutting in
KGd2F7:Tb3+
, the emission spectra were measured under spectrally selective excitation of
Gd3+
and Tb3+
ions through 8S7/2 –
6IJ (=273 nm) and 4f-5d (=210 nm) transitions
respectively. Then the intensity ratios of blue (5D3 –
7FJ) and green (
5D4 –
7FJ) emissions of
Tb3+
were compared in these two spectra because the downconversion effect should result in
relative increase of the green emission intensity compared to the blue one under 4f-5d
excitation of Tb3+
. Also excitation spectra of blue (436 nm) and green (542 nm) emissions
were measured in the spectral range covering both the region of Gd3+
4f-4f absorption and of
Tb3+
4f-5d absorption.
It was found that for samples with Tb3+
concentrations of the order of few at. % the
intensity ratio of blue and green emissions does not depend on excitation photon energy. The
shapes of excitation spectra of blue and green emissions of Tb3+
are identical in the whole
studied excitation range. For higher concentrations of Tb3+
(5-10 at. %) the intensity of blue
emission is two orders of magnitude lower than that of green emission and accordingly the
quantitative comparison of intensity ratio of two emissions cannot be performed with high
enough accuracy. For even higher concentrations of Tb3+
the blue emission is practically
absent. Thus, our experimental results did not confirm the presence of quantum cutting
through downconversion in the studied gadolinium fluoride crystals singly doped with Tb3+
.
[1] R.T. Wegh, H. Donker, E.V.D. van Loef, K.D. Oskam, A. Meijerink, J. Lumin. 87–89,
1017 (2000).
[2] R.T. Wegh, E.V.D. van Loef, A. Meijerink, J. Lumin. 90, 111 (2000).
[3] T.-J. Lee, L.-Y. Luo, E. W.-G. Diau, T.-M. Chena, B.-M. Cheng, C.-Y. Tung, Appl. Phys.
Lett. 89, 131121 (2006).
[4] H.-Y. Tzenga, B.-M. Chengb, T.-M. Chen, J. Lumin. 122–123, 917 (2007).
119
PI_11 Coherent cooperative fluorescence resonance energy transfer
S. K. Sekatskii
1), K. K. Pukhov
2)
1)
Laboratoire de Physique de la Matière Vivante, IPSB, BSP, Ecole Polytechnique Fédérale
de Lausanne, Lausanne, CH 1015, Switzerland
E-mail: [email protected]
2)
Laser Materials and Technology Centre of General Physics Institute of Russian Academy of
Sciences, 38 Vavilova St., Block “4”, Moscow 119991, GSP-1, Russia
Cooperative fluorescence resonance energy transfer (cooperative FRET) has been
discovered experimentally first by Basiev, Doroshenko and Osiko for the transitions from
Nd3+
2/15
4
2/3
4 IF (donor) to Ce3+
2/7
2
2/5
2 FF (acceptor) in
3
31 : NdFCeLa xx crystals
[1] (see also [2] for cooperative FRET from Ho3+
and Tm3+
to Ce3+
) and later on by Vergeer
et al. for the transitions from Tb3+
6
7
4
5 FD (donor) to Yb3+
2/5
2
2/7
2 FF (acceptor) in
3
41 :TbPOYYb xx crystals [3]. Here we predict that for similar crystals, the coherent
cooperative fluorescence resonance energy transfer process at low (liquid helium)
temperatures could be observed: an electronic excitation, which is initially localized at one
rare-earth ion, in appropriate conditions is fully or partially transferred to two neighboring
rare-earth ions without the loss of coherency thus forming entangled quantum state of three
ions.
Based essentially on earlier theoretical works of Kushida [4], where non-coherent
cooperative FRET rate for Tb-Yb-Yb ions with the mutually equal interionic distances equal to
0.37 nm (YPO4 crystal case) has been calculated, we consider coherent FRET rate for this
system. The characteristic coherent FRET time around 500 – 1000 ns, hence reasonably
shorter than the characteristic decoherence time for similar optical transitions at liquid helium
temperatures, has been derived. Certainly, large decoherence times imply rather narrow
spectral lines which might make questionable the possibility of an energy coincidence
between the optical transitions of donor and neighboring acceptors involved into the coherent
cooperative FRET. However, recent achievements in “crystal engineering” (very broad class
of different RE containing crystals, ceramics and nanoparticles available today), as well as
existing broad possibilities to adjust the spectra applying local magnetic and (especially)
electric fields to the crystal, hold much promise in this direction: situation is indeed the same
as with our recent proposal concerning coherent FRET quantum computing controlled by
Scanning Probe Microscope [5].
An inverse process, that is the coherent up-conversion where the excitation energy of two
acceptor centers is resonantly summed up on one donor center, can be analyzed for the
transitions involved along the same lines. Such an analysis readily demonstrates the feasibility
of this process for the same crystals and experimental conditions. We believe that these
effects are not only of a fundamental interest but that they will find use in a rapidly emerging
field of the rare-earth ions-based quantum informatics.
[1] T. T. Basiev, M. E. Doroshenko, and V. V. Osiko, JETP Lett. 71 (2000) 8.
[2] T. T. Basiev, M. E. Doroshenko, V. V. Osiko, and A.M. Prokhorov, JETP 93 (2000)
1178.
[3] P. Vergeer, T. J. H. Vlugt, M. H. F. Kox, et al., Phys. Rev. B71 (2005) 014119.
[4] T. Kushida, J. Phys. Soc. Jap. 34 (1973) 1318; 1327; 1334.
[5] S. K. Sekatskii, M. Chergui and G. Dietler, Europhys. Lett. 63, (2003) 21.
120
PI_12 Enhancement of hypersensitive transitions of rare-earth ions caused by an
Optical Near Field of nanoobjects
K.K. Pukhov1)
, S.K. Sekatskii2)
1)
Laser Materials and Technology Centre of General Physics Institute of Russian Academy of
Sciences, GSP-1 119991, 38 Vavilov St., Block “D”, Moscow, Russia 2)
Laboratoire de Physique de la Matière Vivante, IPSB, BSP, Ecole Polytechnique Fédérale
de Lausanne, CH 1015, Lausanne, Switzerland
The hypersensitive nature of certain transitions of rare-earth (RE) ions is known for a long
time [l]. The very name of this phenomenon witnesses a strong dependence of characteristics
of these transitions on environment properties thus making them a prospective tool to be used
as a sensitive reporter of these same properties, e.g. local variations and changes of the
medium refraction index – the task which nowadays becomes more and more important, e.g.
in biophysical and biochemical researches. In this Note we analyze an enhancement of
hypersensitive transitions caused by optical near-field of nanoparticles.
In Ref. [2], Judd has analyzed the earlier proposed so called inhomogeneous dielectric [3] and
dynamic coupling [4] mechanisms of the hypersensitivity, demonstrated their equivalency and
gave clear physical interpretation of the phenomenon. Most importantly, he showed that the
ligand field effect on the corresponding radiation transition rate amounts to the following
increase of an electric dipole moment of the rare earth ion: 3
,
/s sa sa
s a
e D , where e is an
elementary charge; γs – the polarizability of s-th ligand supposing the isotropic polarization,
and sa - the vector connecting s–th ligand with a–th electron of the RE ion. In light of the
quite known circumstance that in the frame of an electrostatic approximation, a spherical
nanoparticle, subject to incoming plane electromagnetic wave, creates an additional field
equivalent to an electric dipole field, a similarity of this problem to the hypersensitive
transition problem considered by Judd becomes quite evident. Taking into account such a
similarity and allowing for the specificity of 4f states, we have determined the following Judd
– Ofelt transition intensity parameter for RE ion residing near a nanoparticle:
22 2
2 2
28
15 2
NP med
NP med NP
r
R
. (1)
Here NP and med are dielectric permittivity of nanoparticle and medium respectively, <r2> is
the mean square 4f-electron radius averaged over the 4f wave function, and RNP is the radius
of a nanoparticle. According to Judd-Ofelt theory, the rate of radiative electrical dipole
intermultiplet J →J’ transition is proportional to the line strength
2 2 2(2) (4) (6)
2 4 6( , )S J J J U J J U J J U J . (2)
Hypersensitive transitions are characterized by large values of the square of reduced matrix
elements (2)J U J , and eq. (1) readily enables to estimate the enhancement of
hypersensitive transitions of RE ions caused by an optical near field of nanoobjects.
[1] B. Judd, Phys. Rev. 127, 750 (1962).
[2] B.R. Judd, Physica Scripta 21, 543 (1980).
[3] C. K. Jørgensen, B.R. Judd, Mol. Phys. 8, 281 (1964).
[4] T.R. Faulkner, F.S. Richardson, Mol. Phys. 35, 1141 (1978).
121
PI_13 Host cations contributions to VUV excitation spectrum
of Ce3+
ions 5d-4f fluorescence in LiY1-xLuxF4 crystals
L. A. Nurtdinova1)
, K. Ivanovskikh2)
, V. V. Semashko1)
, M. F. Joubert2)
, S. L. Korableva1)
1)
Kazan Federal University, 18 Kremlevskaya str., 420008 Kazan, Russia 2) Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622
Villeurbanne cedex, France
Scheelite-type double-fluoride LiY1-xLuxF4 (x=0…1) crystals doped by Ce3+
ions are well-
known and effective active media for tunable solid-state lasers [1]. However their laser
efficiency limited by color center absorption arising under UV pumping because of step-wise
two photon ionization of activator ions. Besides due to excited-state absorption from Ce3+
ions 5d-state Ce3+
: LiY1-xLuxF4 crystals containing Lu3+
ions demonstrate higher 5d-4f
fluorescence quantum yield when excited at the wavelengths shorter than ~300 nm as
compared with Ce:LiYF4 [2]. These experimental facts stimulate studies of the influence of
cationic composition of the host on relaxation dynamics of excitation energy in Ce3+
: LiY1-
xLuxF4 crystals.
The experiments were performed on Ce:LiYF4, Ce:LiLuF4 and mixed Ce:LiY0,4Lu0,6F4
crystals grown by Bridgman-Stockbarger technique in Kazan Federal University.
Time-resolved Ce3+
ions 5d-4f fluorescence excitation spectra and Ce3+
fluorescence
decays under different excitation wavelength were registered on the SUPERLUMI setup
(HASYLAB, DESY). Excitation was performed by 130 ps pulses of synchrotron radiation in
the range 55-335 nm. Samples emission was detected with high-speed R3809U-50S
microchannel plate photomultiplier. Time-resolved spectra were recorded within two time
windows (TW): 2-14 ns (fast TW) and 72-172 ns (slow TW). Time-integrated spectra were
recorded by integrating signal within 192 ns. The measurements were performed at T = 295-
300 K.
Analysis of Ce3+
ions 5d-4f fluorescence decays features together with time-resolved
excitation spectra allowed to reveal channes of energy transfer to Ce3+
ions associated with
Li+, Y
3+ and Lu
3+ host cations. Ce
3+ ions levels positions within the band gap and energy
transfer mechanisms under excitation below 11 eV were established. Ce3+
ions 5d-4f
fluorescence quantum yield and fluorescence decays in Ce:LiYF4, Ce:LiLuF4 and mixed
Ce:LiY0,4Lu0,6F4 crystals under excitation in 4-6.5 eV range are presented and discussed.
[1] L. A. Nurtdinova, V. V. Semashko, O. R. Akhtymov, S. L. Korabieva, M. A. Marisov,
“New all-solid-state tunable UV Ce3+
,Yb3+
:LiY0.4Lu0.6F4 laser”, Pis'ma v ZhETF, 96, 706-708
(2012).
[2] A.S. Nizamutdinov_, V.V. Semashko, A.K. Naumov, S.L. Korableva, R.Yu.
Abdulsabirov, A.N. Polivin, M.A. Marisov , “Optical and gain properties of series of crystals
LiF–YF3–LuF3 doped with Ce3+
and Yb3+
ions”, J. Lumin., 127, 71-75 (2007)
122
PI_14 Yb2+
and Yb3+
optical centers in double-doped Ce3+
,Yb3+
:SrAlF5 single crystals
A. N. Yunusova 1)
, V. V. Semashko 1)
, G. M. Safiullin 2)
, M. A. Marisov 1)
1)
Kazan Federal University, 420008, 18 Kremlevskaya street, Kazan, Russia 2)
Zavoisky Physical-Technical Institute, 420029, 10/7 Sibirsky tract, Kazan, Russia
SrAlF5 crystals doped by rare-earth ions, especially Ce3+
, is a very promising laser material
for the UV/VUV spectral ranges. Nevertheless, as the most fluoride crystal hosts SrAlF5
crystals are subjected to the strong coloration under pumping condition (e.g. [1]). Considering
the fact that co-doping by Yb3+
ions lead to suppression of color centers formation process in
cerium-doped crystals [2], double-doped Ce3+
,Yb3+
:SrAlF5 crystals were investigated.
For the first time 4f↔5d and 4f↔4f luminescence and excitation spectra of Yb3+
и Yb2+
ions in double-doped Ce3+
,Yb3+
:SrAlF5 single crystals were studied. Similar to situations with
Ce3+
ions, heterovalent substitution of Yb3+
→ Sr2+
cations in double-doped Ce3+
,Yb3+
:SrAlF5
crystal leads to four optically nonequivalent centers formation. Additionally, during growth
process Yb3+
ions partially incorporate into the crystal host in divalent state, and position of its
luminescence and excitation bands is in agreement with results reported for Yb2+
:SrAlF5
crystals [3]. Experimental Stark energy sub-level diagrams for optically nonequivalent Yb2+
and Yb3+
optical centers in double-doped Ce3+
,Yb3+
:SrAlF5 single crystals are suggested.
In luminescence spectra broad band near 500 nm corresponding to color centers
disappears in double-doped Ce3+
, Yb3+
:SrAlF5 samples, consequently co-doping lead to the
sufficient suppression of color centers as expected.
In the context of possibility to obtain lasing on 5d-4f intraconfigurational transitions of
Ce3+
ions in SrAlF5 crystal host co-doping by Yb3+
ions do not reveals any significant
differences in energy state structure of impurity cerium centers both in luminescence and
excitation spectra for single Ce3+
:SrAlF5 and double-doped Ce3+
,Yb3+
:SrAlF5 crystals.
Prospects of using Ce3+
,Yb3+
:SrAlF5 crystal as an active medium of UV solid-state laser
are discussed.
This investigation was supported by the Federal target program “Scientific and research
and educational personnel of innovational Russia” ( 16.740.11.0638).
[1] M. Laroche, S. Girard, R. Moncourge, M. Bettinelli, R. Abdulsabirov, V. Semashko,
Beneficial effect of Lu3+
and Yb3+
ions in UV laser materials, Opt. Materials 22, 147-154
(2003).
[2] V. V. Semashko, B. M. Galyautdinov, M. A. Dubinskii, R. Yu.Abdulsabirov, A.K.
Naumov, S. L.Korableva, Anti-solarant co-doping of Ce-activated tunable UV laser materials,
in Proceedings of the International Conference on LASERS 2000, V.J. Corcoran and T.A.
Corcoran, eds., (Albuquerque, NM, Dec. 4-8, 2000), pp. 668 - 674.
[3] E.W. Henderson, J.P. Meehan, Optical properties of divalent rare-earth ions in SrAlF5, J.
Luminescence. 8, 415-427 (1974).
123
PI_15 Metal Patterns in CaF2 Crystals
R.V. Gainutdinov1)
, A.S. Shcheulin2)
, A.E. Angervaks2)
, P.P. Fedorov3)
, A.I. Ryskin2)
1)
Shubnikov Institute of Crystallography, 119333, Leninskii pr. 59, Moscow, Russian
Federation 2)
National Research University of Information Technologies, Mechanics and Optics, 197101,
Kronverskiy pr. 49, St. Petersburg, Russian Federation 3)
Prokhorov General Physics Institute, 119991, Vavilov str. 38, Moscow, Russian Federation
Heating CaF2 crystals in the reduction atmosphere of metal vapors (additive coloring of
crystal) results in color centers formation due to recombination of anion vacancies and
electrons which are produced on the crystal surface and diffuse into its bulk. Additively
colored crystals contain “simple” (F, M, R and N) centers, which are composed of 1–4 anion
vacancies, respectively, with an equal number of electrons and highly-aggregated centers. It
was initially proposed that such centers are colloidal particles of calcium, which arise as a
result of transformation of large accumulation of anion vacancies and electrons into metal
inclusions (see [1]). It was recently found that actually these centers are two-dimensional
rounded or prolate metal islands with thickness of 1.3–1.4 nm and lateral size of 30–200 nm
[2,3]. The islands occur at vacancies/electrons concentration ~1017
cm-3
. When this
concentration increases up to ~1018
cm-3
islands coalesce forming film fragments with pores
of arbitrary shape and different size; the height of these fragments remains equal to 1.3–1.4
nm. Absorption spectrum of such crystals practically contains only the band of “colloidal”
centers (the maximum of this band is within the wavelength range of = 550–650 nm). That
means the most of color centers are “colloidal” particles scattered randomly over the crystal
volume and only their small part form film fragments. Absorption spectrum of crystals with
even higher concentration of color centers changes drastically: the intensity of the absorption
band of “colloidal” centers decreases, and intense non-selective absorption arises typical for
thin metal films. In such a crystal a majority of color centers are coalescent into fragments of
such films. Under impact of the radiation resonant to absorption bands of particular color
centers and the temperature the conversion of centers occurs [4]. Their photochromic
transformations underlie using CaF2 crystals with color centers as highly-stable volume
holographic media [5,6]. The specific diffusion-drift mechanism of hologram recording
results in accumulation of color centers in the minima of fringe pattern; the larger the
exposure the narrower are the regions of centers concentration [7,8]. This feature favors metal
inclusion formation. Thus, recording holograms in additively colored CaF2 crystal with
sufficiently high concentration of anion vacancies/electrons can convert it into a
metamaterial-like state.
[1] W. Hayes, ed., Crystals with the Fluorite Structure: Electronic, Vibrational, and Defect
Properties (Clarendon Press, Oxford, UK, 1974).
[2] R.V. Gainutdinov et al., Phys. Solid State, 53, 1484 (2011).
[3] A.E. Angervaks et al., Appl. Surf. Sci., 267, 112 (2013).
[4] A.E. Poletimov et al., Opt. Spektrosk., 70, 1030 (1991) (in Russian).
[5] A.S. Shcheulin et al., Opt. Spectrosc., 103, 651 (2007).
[6] A.S. Shcheulin et al., Opt. Spectrosc., 103, 655 (2007).
[7] A.V. Veniaminov et al., J. Opt. Soc. Am. B, 29, 335 (2012).
[8] A.S. Shcheulin et al., Opt. Spectrosc., 113, 638 (2012).
124
PI_16 Rare-Earth Ion Reduction under Additive Coloring of CaF2:RE3+
Crystals
A.S. Shcheulin, A.E. Angervaks, T.S. Semenova, L.F. Koryakina, M.A. Petrova,
A.I. Ryskin
National Research University of Information Technologies, Mechanics and Optics, 197101,
Kronverkskiy pr. 49, St. Petersburg, Russian Federation
E-mail: [email protected]
Heating as-grown CaF2:RE3+
crystals in the reduction atmosphere of calcium vapor (additive
coloring of crystals) is an effective technique of RE3+
ions conversion into a bivalent state.
Two opposite processes take place on the surface of the colored crystals: building-up the
surface and its decomposition, the former process being prevalent. As a result, two flows arise
directed from the surface into the bulk: fluorine vacancies and electrons supplied by Ca atoms
in vapor phase that participate in building-up the surface. When coloring of pure (undoped)
CaF2 crystals, these components recombine at crystal cooling with formation of various-type
color centers. When coloring RE-doped crystals, electrons are captured by these ions thus
reducing them up to bivalent state whereas vacancies recombine with interstitial F ions that
compensate extra +1 charge of RE3+
ions; less effective process of color center formation
unfolds after RE ion reduction is finished. Three features of RE-doped crystals coloring as
compared with pure crystals are as follows: (1) sharp slowing-down the coloring rate, (2)
sharper border between colored and non-colored segments of the colored sample and (3)
larger concentration of vacancies/electrons that can be introduced into the crystal during the
coloring procedure [1–3]. The degree of diffuseness of a boundary between the colored and
non-colored segments of the sample is determined by the diffusion free path of the vacancy,
which is limited in RE-doped crystals by its recombination with interstitial F ions. Slowing-
down of the coloring rate is due to the process of thermal ionization of RE2+
ions in the
colored segment of the sample. The released electrons recombine with anion vacancies, which
arise due to Frenkel pair’s formation whereas F
components of the pairs restrict the diffusing
vacancy’s free path. A sharp boundary between colored and non-colored segments in RE-
doped crystals indicates a threshold character of the dependence of the free path of a vacancy
on the reduction degree. Apparently, the threshold is reached when the concentration of
compensating interstitial F ions becomes comparable to the concentration of F
ions –
components of Frenkel pairs. The concentration of vacancies/electrons that can be introduced
into the crystal is determined by the difference in production of these components on the
surface and in the bulk at given coloring conditions. The sources of these components in the
bulk are thermally ionized color centers (activation energy of ~1 eV) for the pure crystals and
thermally ionized RE2+
ions for electrons (activation energies are in range of 0.9–4.0 eV) and
Frenkel pairs for vacancies (activation energy of 2.7 eV) for RE-doped crystals. Such large
difference in activation energies of these processes for pure and RE-doped crystals is
responsible for the much higher concentration of these components in RE-doped CaF2
crystals.
[1] A.S. Shcheulin, T.S. Semenova, A.I. Angervaks, A.I. Ryskin., Opt. Spectrosc. 108, 964
(2010).
[2] A.S. Shcheulin, A.E. Angervaks, T.S. Semenova, L.F. Koryakina, M.A. Petrova, A.I.
Ryskin, Opt. Spectrosc. 110, 617 (2011).
[3] A.S. Shcheulin, A.E. Angervaks, T.S. Semenova, L.F. Koryakina, M.A. Petrova, P.P.
Fedorov, V.M. Reiterov, E.A. Garibin, A.I. Ryskin, Appl. Phys. B. In press.
125
PI_17 Effect of Ce ions on the spectral and decay characteristics of
Li2O-B2O3-P2O5-CaF2 glasses doped with rare-earth ion
D.T. Valiev 1), E. F. Polisadova
1), K. N. Belikov
2), N. L. Egorova
2)
1
National Research Tomsk Polytechnic University 634050, Lenin Avenue 30, Tomsk,
Russian Federation 2 Institute of Single Crystals NAS of Ukraine, 61001 Kharkov, Lenin Avenue 60, Ukraine
E-mail: [email protected]
The creation of new materials with specific optical properties requires an understanding of
the mechanisms of luminescence in different systems, processes for electronic excitations
between the emission centers and the glass matrix, the interaction of activated ions between
them. Activated by rare-earth ions (Ce, Tb, Gd) glasses are promising materials for the
creation of ionizing radiation detectors, photo-and thermo-luminescent dosimeters [1, 2].
However, the development of optimal glass compositions, selection of cation-modifier to
improve the physicochemical properties of the glass does not become outdated.
The purpose of this study is to investigate the influence of ions Ce3+
on the spectral and
kinetic characteristics of luminescence glass doped with gadolinium and terbium ions. The
mechanisms of energy transfer in co-doped glasses by spectrometry with time resolution was
investigation.
In this work we studied glasses of composition Li2O-B2O3-P2O5-CaF2 (LBPC), doped of
Tb3+
, Gd3+
and co-doped Ce3+
. The samples were synthesized at the Institute for Single
Crystals of National Academy of Sciences of Ukraine (Kharkiv). The resulting glasses are
characterized by homogeneity, good transparency and moisture resistance. They are
characterized by low melting point, high solubility of rare-earth components.
Ultraviolet-visible transmission spectra of glasses were measured using a
spectrophotometer «LOMO Photonica» SF-256 UVI in the spectral range 200-1000 nm.
Pulsed cathodoluminescence (PCL) spectra and decay kinetic characteristics of luminescence
were measured on the installation described detail in [3]. The samples were excited by small-
size high-current electron accelerator, being a part of pulsed optical spectrometer.
It was found that decay time of luminescence Gd3+
in band 312 nm sample doped Gd and
Ce considerably shorter than in it doped only Gd: 1,7 and 3,3 ms respectively. Decay time of
band 312 nm don’t vary at co-doping glass by ions Gd and Pr. Narrow band λmax = 340 nm
and wide band λmax ≈ 355 nm is observed in emission spectra of Ce3+
-doped glasses. Decay
time of luminescence Ce3+
is about 50 ns. It was found that lifetime of Tb3+
emission levels
have been increasing in the presence the Ce3+
ions in glass sample. It was show that the
luminescence intensity of UV and visible range of spectrum is significantly changing from
impurity composition of samples. It is that In the glasses containing ions Tb3+
and Ce3+
,
significantly increases the decay time of the emission bands at 436, 545, 620 nm, compared
with the samples doped with ions alone Tb3+
was established, in the kinetics of luminescence
decay of LBPC is observed rise of the emission intensity takes place after the end of the
excitation pulse. The mechanism of energy transfer in phosphate-borate-fluoride glasses
doped with rare elements are discussed.
The work was supported by the Ministry of Education, direction «Science» (project
2.3302.2011)
[1] G. Blasse, B.C. Grabmeier (1994). Luminescent Materials. Springer Verlag, Berlin 232 p.
[2] M. Nikl Scintillation detectors for X-rays. Meas. Sci.Technol. (2006) pp.17-37.
[3] Korepanov V. I., Lisitsyn V. M. and Oleshko V. I. High-current nanosecond electron
beams for probing the parameters of solids // Russian Physics Journ. V. 43, No. 3 (2000)
pp.185-191.
126
PI_18 The spectral and decay characteristics of luminescence of nano- and
microcrystals of ZnWO4 in the polymer matrix
V. M. Lisitsyn, E.F. Polisadova1), D.T. Valiev
1), I. A. Tupitsina
2), L.A. Andryushenko
2),
A.M. Dubovik2), A.G. Yakubovskaya
2)
1
National Research Tomsk Polytechnic University 634050, Tomsk, Lenin Avenue30, Russia 2 Institute of Scintillation Materials NAS of Ukraine, 61001 Kharkov, Lenin Avenue 60,
Ukraine
E-mail: [email protected]
Materials in the form of nanocrystals dispersed in a polymer matrix are promising elements
in creating elements of practical optoelectronics, including the discovery of new high-
performance scintillator cause an increased interest of researchers working in the field of
physics and chemistry of low-dimensional systems. Such materials exhibit unusual compared
to bulk materials, the optical and electronic properties [1]. The features of these materials are
defined as the individual properties of the nanocrystals and their interaction with each other
and to the matrix.
The purpose of this study is to investigate the pulse photoluminescence (PPL) and pulse
cathodoluminescence (PCL) of zinc tungstate nanocrystals in polymer matrix order to
establish the dependence of the luminescence characteristics of the size of the phosphor
particles in the nanocomposite.
The test samples were themselves resistant polymer films with low molecular weight
silicone rubber introduced synthesized nanoscale crystals (nanocrystals) ZnWO4 and
desintegrated crystals ZnWO4 to micro-and nano-scale
The samples were excited two kind of sources: pulsed nitrogen laser with a wavelength of
337,1 nm (pulse width: 2.5 ns) and small-size high-current electron accelerator, being a part
of pulsed optical spectrometer [2]. In work spectrometry with time resolution was used.
PPL and PCL spectra studied of materials luminescence in two specific areas: 400 and 490
nm was observed. Emission in area 400 nm is excited by laser radiation and high-energy
electron fluxes. The dependence of the luminescence spectra of the type of excitation was
observed. The method of preparation of input particles and their size depends very much on
the characteristic relaxation time of the luminescence when excited by an electron and laser
pulses.
This work was supported by the State Agency on Science, Innovations and Information of
Ukraine and by the Ministry of Education, direction «Science» (project 2.3302.2011)
[1] Nanotechnology Research Directions for Societal Needs in 2020. Retrospective and
Outlook. Editors: Mihail C. Roco, Chad A. Mirkin, Mark C. Hersam (2010) p.548.
[2] Korepanov V. I., Lisitsyn V. M. and Oleshko V. I. High-current nanosecond electron
beams for probing the parameters of solids, Russian Physics Journal, V. 43, No. 3 (2000)
p.185-191.
127
PI_19 Synthesis and luminescent properties of yttrium niobate X-ray phosphors
activated by europium
A.Yu. Mester1)
, A.N. Trofimov1)
, M.V. Zamoryanskaya1)
1)
Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Saint Petersburg,
Russia
X-ray phosphors are used extensively in industrial and medical radiography. The
development of new more effective X-ray phosphors is necessary to reduce the X-ray
irradiation dose of the patients. This phosphors must have high X-ray absorption coefficient
and high luminescence efficiency. Yttrium niobate activated by europium have this qualities
due to the fact that its matrix effectively absorbs the X-rays and europium has good
luminescent properties. Therefore this phosphor is promising candidate for use in radiography
[1].
In this work YNbO4:Eu3+
X-ray phosphors were synthesized and studies of their luminescent
properties were conducted.
Specimens were prepared by solid-phase baking in the air from homogeneous mixture of
oxides. Yttrium, niobium and europium oxides were thoroughly milled with acetone and then
baked in 3 stages at 900, 1050 and 1200 ⁰C. Between the stages powders were additionally
milled.
The study of the powders by X-ray powder diffraction method showed that samples are
single-phased. Research of the element composition of samples was conducted using electron
probe microanalysis. Luminescent spectra and decay times of the main radiation bands were
studied by local
cathodoluminescence method. As a
result the luminescence intensity
dependence on concentration of
europium was obtained. Also
histograms of grain size distribution
were constructed by using scanning
electron microscopy method. A
comparison of luminescent properties
of the powders with luminescent
properties of commonly used in
radiography phosphors was carried
out.
[1] M. Nazarov, Y.J, Kim, et al., J.
Appl. Phys. 107, 103104 (2010).
Fig.1 Luminescent spectrum of YNbO4:Eu3+
128
PI_20 The influence of the magnetic field strength and excitation intensity
on the shape of microphotoluminescence spectra and paramagnetism
of impurities in crystalline ZnO films doped with Sm, Eu, Er
Yu.A. Shafir2)
, M.M. Mezdrogina1)
, A. Ja. Vinogradov1)
, I.N. Trapeznikova1)
, O.V.
Koplak3)
, A.J. Dmitriev3)
1)
Ioffe Physico-Technical Institute , Saint-Petersburg, Polytechnicheskaya, 26, Russia 2)
SPbSTU, Saint-Petersburg, Polytechnicheskaya, 29, Russia 3)
Institute of Problems of Chemical Physics, Chernogolovka, Russia
Wide gap semiconductor ZnO attracts a serious attention as functional material for
optoelectronic devices operating in UV- region of spectrum. Extremely large value of exciton
binding (60 meV) at a band gap 3,34eV provides an exciton governed luminescence at short
wavelength (368-390)nm.[1] ZnO crystal was used for growth of GaN/ InGaN structures
with small density of defects. Moreover, ZnO is biosafe and biocompatible material, which
may be used in biomedical applications without additional coating. Doped with rare-earth
ions (REI), ZnO crystalline films give promising applications for fabrication of light-emitting
devices (LED) in UV (doping with Tm), visible (Eu,Er) , IR- 1540 nm (doping with Er).
These devices can operate at high temperatures.
The purpose of this work is to investigate the influence of the magnetic field strength and
excitation intensity on the shape of microphotoluminescence spectra and paramagnetism of
impurities in crystalline ZnO films doped with Sm
All ZnO films investigated in this work according to x-ray diffraction analysis were
crystalline, prepared by magnetron sputtering ZnO target, under T=520 ºC, in gas mixture
Ar+O. Crystalline Si plates with crystalline SiC thin films (about 20 nm) were used as
substrates for minimization of mismatching tension between c-Si and ZnO. ZnO bulk crystals
were obtained by gas-phase growth, density of dislocation was equal 10 cm-2
. Diffusion
technique was used for doping with this impurity. Concentration of Sm was measurement by
x- ray fluorescent technique on the lines Kα and was the same (around 5·1018
cm-3
) as in
MQW structures on the base of InGaN/GaN. Doping impurity Sm as an isovalent impurity
was used in investigations of MQW structures on the base of InGaN/GaN. It is known Sm 3+
ion substitutes Ga3+
in GaN (AIII
BV
compound). ZnO belongs to AII
B VI
compounds, and
Sm3+
is not isovalent impurity. In this case for realization of intracenter 4f transitions in Sm3+
,
additional concentration (in compare with undoped semiconductor matrix) of vacancies VO is
necessary. Laser with λ = 266 nm, excitation power was equal to W= 3,52 10 23
photon s/ cm2.
Magnetic field in Faraday geometry in the range of 0-5 T was provided by superconducting
solenoid. PL spectra of bulk ZnO crystals and undoped crystalline ZnO films are similar:
values of luminescence intensity I, λMAX = 370nm, FWHM=10meV. There is the shift λMAX in
short wave length λMAX=369,5nm, FWHM=7meV in PL spectra of ZnO: Sm. It was found
with increasing of magnetic field strength the values I in ZnO:Sm films decreased in contrast
to InGaN/GaN:Sm, in which increasing of magnetic field strength leads to increasing I.
Magnetic properties ZnO:Sm films are similar to magnetic properties of structures with MQW
on the base of InGaN-GaN:Sm. Magnetic properties of ZnO:Eu distinguished between
properties of ZnO:Er. Temperature independent paramagnetism as well as Curie like
contribution to the temperature dependence of the magnetization was observed in ZnO:Sm,
ZnO:Eu, ZnO:Er. Field dependence of the magnetization obeys Brilloin function typical for
paramagnetic Sm ions.
These investigations were supported by RFFI grant 13-02-00726a.
[1] M.K.Chong,A.P.Ablassa,K.Pita,S.F.Yu, Appl.Phys.Lett.,93, 151 105,( 2008)
129
PI_21 The sensitization of Ln3+
luminescence in [2.2]paracyclophane-derived
β-diketonates
I.S. Pekareva1)
, L.N. Puntus1,2)
, K.A. Lyssenko2)
, F. Kajzar3)
1)
Kotel’nikov Institute of Radioengineering & Electronics, Russian Academy of Sciences,
125009, 11-7 Mokhovaya, Moscow, Russia 2)
A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
119991, 28 Vavilov St, Moscow, Russia 3)
Université d’Angers, Institut des Sciences et Technologies Moléculaires d'Angers,
MOLTECH Anjou - UMR CNRS 6200, 2, Bd Lavoisier, 49045 Angers cedex, France
E-mail: [email protected]
From a fundamental standpoint [2.2]paracyclophane (PCP) is composed of two
benzene rings covalently fixed in a “face-to-face” geometry by ethano bridges. The
introduction of various substituents in this molecule can easily change its optical properties by
means of the energy change of “transannular charge transfer” state. In one's turn the
extremely sharp emission lines and high luminescence quantum yield of the lanthanide ions
(Ln) make the lanthanide complexes the perfect candidates for the different applications in the
fields of electronics and photonics. In order to fully utilize the benefits of the lanthanide ions
and substituted PCP a series of lanthanide [2.2]paracyclophane-derived β-diketonates (β-dik)
with different donor-acceptor properties of functional groups (R) and with content Ln(β-
dik)3phen (where Ln=Eu, Gd, Tb, Sm, Pr, Dy, Nd and phen – 1,10-phenanthroline) was
designed and synthesized (Fig.1). Luminescence properties of these Ln complexes were
studied by optical spectroscopy including absorption, excitation, luminescence and
phosphorescence spectra as well as the lifetime measurements of excited states.
Figure 1. General view of lanthanide [2.2]paracyclophane-derived β-diketonates. PCP marked
by a dashed cycle
The value of intrinsic quantum yield of the Eu3+
ion in the studied β-diketonates varies
from 15 to 60% while the lifetime that of from 0.12 to 0.62 ms. The introduction of functional
groups with different donor-acceptor properties in [2.2]paracyclophane-derived -diketones
leaded to the red shift of “transannular charge transfer” band up to 400 nm. The contributions
of the different charge transfer states including intraligand and stacking induced charge
transfer state as well as back energy transfer process in the luminescence sensitization of the
Ln3+
ion were analyzed. Importantly the designed complexes are perspective for the different
optical applications in both visible and NIR region.
This work is supported by the Russian Foundation for Basic Research (grants N12-03-
00107, 13-03-01041) and by the Council on Grants at the President of Russian Federation
(Program for State Support of Young Doctors of Science, Project MD-1020.2012.3).
PCP
130
PI_22 Studying the energy dependence of intrinsic conversion efficiency
of single crystal scintillators under X-ray excitation
N. Kalyvas, I. Valais, S. David, Ch. Michail, G. Fountos, P. Liaparinos, I. Kandarakis
Technological Educational Institute of Athens/Department of Medical Instruments
Technology, 12210 Egaleo Athens, Greece
E-mail: [email protected]
Single crystal scintilators are used in various radiation detectors applications. The efficiency
of the crystal can be determined by the Detection Optical Gain (DOG) defined as the ratio of
the emitted optical photon flux over the incident radiation photons flux. A parameter
affecting DOG is the intrinsic conversion efficiency (nC) giving the percentage of the X-ray
photon power converted to optical photon power. nC is considered a constant value for X-ray
energies in the order of keV [1] although a non-proportional behavior has been reported [2,3].
In this work an analytical model, has been utilized to single crystals scintillators GSO:Ce,
LSO:Ce and LYSO:Ce to examine whether the intrinsic conversion efficiency shows non
proportional behavior under X-ray excitation.
DOG was theoretically calculated as:
max
0
max
0
)(),,()/()()(E
E
E
E
CQ EfnkGEEnEnEfDOG ,
where f(E) is the spectral component of energy E, of the incident X-ray spectrum, nQ(E) is the
X-ray absorption efficiency, Eλ is the energy of the produced optical photons of wavelength λ
and G(k,n,λ) is the light transmission efficiency. n is the refractive index of the crystal and k is
the light loss percentage per mm in the crystal [4]. The theoretical DOG values were
compared with experimental values obtained by irradiating the crystals with X-rays at tube
voltages from 50 to 140 kV and by measuring the light energy flux emitted by the irradiated
screen. An initial value for nC (obtained from literature data) was assumed for the X-ray tube
voltage of 50kV. For the higher X-ray tube voltages the optical photon propagation
phenomena was assumed constant and any deviations between experimental and theoretical
data were associated with changes in the intrinsic conversion efficiency. The experimental
errors were below 7% for each experimental setup.
The behavior of nC values for LSO:Ce and LYSO:Ce were found very similar, i.e. ranging
with values from 0.089 at 50kV to 0.015 at 140kV, while for GSO:Ce, nC demonstrated a
peak at 80kV.
Acknowledgement
This research has been co-funded by the European Union (European Social Fund) and Greek
national resources under the framework of the “ARISTEIA” project MISCIRLU code 1476 of
the “Education & Lifelong Learning” Operational Programme.
[1] Kalivas N., Valais I., Nikolopoulos D., Konstantinidis A.: et al.(2007), “Light emission
efficiency and imaging properties of YAP:Ce granular phosphor screens” Appl. Phys. A, Vol
89, pp 443-449
[2] Moses W.W., Payne S.A., Choong W-S., Hull G., Reutter B.W. (2008) “Scintillator Non-
Proportionality: Present Understanding and Future Challenges” IEEE TNS Vol 55, pp1049-
1053
[3] Khodyuk I.V., de Haas J.T.M. and Dorenbos P. (2010) “Nonproportionality Response
Between 0.1-100keV Energy by Means of Highly Monochromatic Synchrotron X-rays” IEEE
TNS Vol57, pp.1175-1181.
[4] Nikolopoulos D., Kalyvas N., Valais I., et al.: “A semi-empirical Monte Carlo based
model of the Detector Optical Gain of Nuclear Imaging scintillators”, JINST, 7, P11021, 2012
131
PI_23 Characterisations of new Nd3+
-doped scheelite-type molybdates
for laser materials
M. Guzik1)
, E. Tomaszewicz2)
, Y. Guyot3)
, P. Tomaszewski4)
, J. Legendziewicz1)
, G. Boulon3)
1Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, PL-50-383 Wroclaw, Poland
2Department of Inorganic and Analytical Chemistry, West Pomeranian University
of Technology, Al. Piastów 42, PL- 71-065 Szczecin, Poland 3Institute Light Matter, UMR5306 CNRS-University of Lyon1, University of Lyon, 69622
Villeurbanne, France 4Institute of Low Temperature and Structure Research,PAS,Okolna 2,50-422 Wroclaw,Poland
The necessity to develop new laser materials was our motivation to study a new family of molybdates
activated by the Nd3+ ions, which crystallizes in the scheelite-type structure (the tetragonal symmetry,
the space group I41/a). A series of Cd1-3xNd2x xMoO4 solid solutions with concentration of Nd3+ ions
from 0.1 mol% to 66 mol% with respect Cd2+ ions have been successfully synthesized by a high-
temperature annealing, using CdMoO4 and Nd2(MoO4)3 as the starting materials. Structural and
spectroscopic characterizations of Nd3+ in substitution of Cd2+ were carried out. The Nd3+ ions in this
matrix most probably occupy two non-equivalent symmetry sites (see Fig.1). The substitution of Cd2+
by trivalent Nd3+ cations leads to the formation of cationic vacancies in a framework (which are
denoted in the chemical formula as ) and its concentration depends essentially on the composition of
initial CdMoO4/Nd2(MoO4)3 mixtures. The analysis of the morphology using SEM reveals high
homogeneity of the spherical-shape products with the average grain size of about 10 m. The optical
analysis and the laser performance parameters suggest Cd1-3xNd2x xMoO4 as a potential laser powder
material: both the values of the absorption cross-section and the very strong emission of the 4F3/2 4I11/2 laser channel of Nd
3+ recorded under Xe lamp excitation or OPO laser pumping, as well as, the
radiative lifetimes of IR luminescence are appropriate for potential applications of this phosphor as a
solid-state laser. Our earlier studies have shown that the presence of the cationic vacancies in the
framework may significantly improve the laser parameters [1].
[1] M. Guzik, E. Tomaszewicz, Y. Guyot, J. Legendziewicz, G. Boulon, J. Mat. Chem. 22
(2012) 14896-14906.
Fig. 1 (a) The structure of low-polymorphic modification of Cd1-3xNd2x xMoO4 solid solutions, (b)
Selected transitions (4I9/2→2P1/2, and 4I9/2→
4F3/2) of the absorption spectra of Cd1-3xNd2x xMoO4 (5%
Nd3+) at 298 and 4K, (c) Emission spectra of Cd1-3xNd2x xMoO4 (3% Nd3+) under different Ti-
Shappire laser exciation at 77K.
1050 1060 1070 1080 1090 1100
0
50000
100000
4F3/2
4I11/2
nm
Lu
min
esce
nce
inte
nsity
(a
.u.)
exc 5-23 732,25 nm
exc 5-39 732,62 nm
exc 5-45 732,76 nm
77K
Cd1-3xNd2xxMoO4 (3% Nd3+
)
430 432 434 436 438 440
Cd1-3xNd2xxMoO4 (5% Nd3+)
23110 cm-1
nm
Ab
so
rba
nce
(a
.u.)
Ecm
23127
2P
1/2
870 880 890 900
RT
4K
11382cm-1
4F
3/2
11455 cm-1
132
PI_24 Phonon spectra of YTiO3 and Y2Ti2O7: ab initio calculations
V.A. Chernyshev, V.P. Petrov, A.E. Nikiforov
Ural Federal University, 620002, Ekaterinburg, Russia
E-mail: [email protected]
Yttrium titanate with pyrochlore structure Y2Ti2O7 attracts attention as a perspective matrix
for rare earth activation [1]. Phonon spectum of the crystal was investigated experimentally
[2] partly. We made ab initio calculation of the spectrum within a periodic approach using
the CRYSTAL09 program package by hybride DFT and Harthree-Fock methods with all-
electron Gaussian-type basis sets.
Phonon spectrum and crystal structure of YTiO3 have been calculated at the same ab initio
methods too. Pressure influence on the crystalline structure have been investigated up to 30
GPa. The best results provided by hybrid functional DFT B3LYP. It is shown, that exchange
interaction can be taken to account at Harthree-Fock formalism.
Elastic modules of Y2Ti2O7 and YTiO3 have been defined at this calculations too.
Static orbital structure of YTiO3 have been defined by pressure influence.
[1] S. A. Klimin, M. N. Popova, E. P. Chukalina, B. Z. Malkin, A. R. Zakirov, E. Antic-
Fidancev, Ph. Goldner, P. Aschehoug, G. Dhalenne , Phys. of the Solid State, 47 (2005) 1425-
1430.
[2] M.T. Vandenborre, E. Husson, J.P. Chatry, D. Michel, J. Raman Spectrosc. 14 (1983) 63-
71
133
PI_25 Valence states of cations in nanostructured transition metal oxides
studied by means of soft X-ray absorption spectroscopy
V. V. Mesilov, V. R. Galakhov, B. A. Gizhevskii
Institute of Metal Physics, Ural Division of the Russian Academy of Sciences, 620990,
S. Kovalevskaya str. 18, Yekaterinburg, Russia
E-mail: [email protected]
Valence states of cations in the nanostructured manganites, ferrites, and cobaltites were
studied by means of X-ray absorption spectroscopy and atomic multiplet calculations.
Nanoceramics LiCoO2, Y3Fe5O12 and FeBO3 were prepared from initial coarse-grained
samples by plastic deformation through the uniaxial compression and shear deformation
under pressure. For this purpose, we used a press with a force of 100 ton and Bridgman
anvils. Nanostructured La0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3 were obtained by grinding initial
coarse-grained powder in a ball mill. Time of grinding was varied from 2 to 8 hours for
various parties of powder. The average sizes of crystal grains were estimated from the
broadening X-ray diffraction peaks. The estimated sizes were found to be 20-100 nm.
X-ray absorption spectra of nanostrucrured oxides were measured at Russian-German
beamline at BESSY-II (Berlin, Germany) in surface sensitivity total photoelectron yield
mode. For some samples, spectra were measured at the I511-3 beamline at MAX-II (Lund,
Sweden) in bulk sensitivity total fluorescence yield mode. Atomic multiplets of X-ray
absorption spectra for transition metal ions were calculated taking into account crystal-field
splitting and charge-transfer process.
The experimental X-ray absorption spectra were compared with atomic multiplet
calculations for 3d metal ions. For nanostructured Y3Fe5O12 and FeBO3 obtained by plastic
deformation method (high-pressure torsion), some amount of Fe2+
ions was found. The
concentration of Fe2+
ions was found to be increased with the increase of the degree of plastic
deformation. No new phases were found in these nanostructured ferrites. It was found that
small deformations (pressures up to 5 GPa and angles of anvil rotation up to 30°) lead to the
generation of lithium vacancies in the bulk of nanostructured LiCoO2 and the formation of the
Li2O phase at the surface. The charge compensation occurs at the expense of holes in oxygen
2p states. An increase in the degree of deformation of lithium cobaltite (at a pressure up to 8
GPa) leads to the formation of Co2+
ions. It was found for nanostructured powder
La0.5Ca0.5MnO3 that the increase of deformation leads to the increase of the valence states of
Mn ions at room temperatures. For nanostructured Nd0.5Sr0.5MnO3, manganese ions were
found to be in 2+, 3+, and 4+ states due to competing processes of reduction and oxidation
taking place at grinding. Thus, the materials remain in a single phase. It was established that
X-ray absorption spectra measured in surface and bulk sensitivity modes allow to investigate
nanocrystal grains being both near the surface, and in the bulk of micron and sub-micron-size
particles which form powder.
This work was supported by the Russian Foundation for Basic Research (projects 11-
02-00166 and 11-02-00252), the Ural Division of the Russian Academy of Sciences (project
12-M-23-2032), and the bilateral Program “Russian–German Laboratory at BESSY”.
134
PI_26 Luminescent spectroscopy of triple-charged rare earth ions incorporated
in lead tungstate scintillator crystals
O.V. Chukova, S.G. Nedilko
Physics Faculty, Taras Shevchenko National University of Kyiv, 4-b, acad. Hlushkov Ave.,
03680, Kyiv, Ukraine
Family of tungstate crystals (PbWO4, CdWO4, CaWO4) brings one of the largest sets of
luminescent detecting materials into techniques using equipment for registration of high
energy particles from medical and border pass tomographs to high energy physics.
Improvement of scintillation characteristics of these crystals was achieved by various ways
such as special doping of the crystals with impurity ions, especially with rare earth (RE) ions,
and annealing of the crystals in various atmospheres, e.g. oxygen, argon, air. Usually, more
than one types of emission centres are formed by the RE3+
ions in the tungstate crystals doped
with the RE3+
ions [1-3]. Features of the RE3+
ions incorporation in the tungstate crystal
lattices are under discussion, yet.
The lead tungstate crystals were grown by the Czochralski method using the "Crystal-617"
installation in Ivan Franko Lviv State University at laboratory headed by Prof. M.
Pashkovsky. The blend was synthesized from lead, tungsten and corresponded RE oxides.
The impurity concentrations in the blend were 5x10-2
wt %. Our analysis showed that
impurity concentrations in the grown samples were reduced by about one or two orders of
magnitude. The measurements of reflection, luminescence emission and excitation spectra
were carried out using synchrotron radiation at SUPERLUMI station at HASYLAB (DESY),
Hamburg, Germany (Project # I-20110592) and laser radiation at complex for spectral-
luminescent investigations at R&D Laboratory “Spectroscopy of Condensed State of Matter”
of Physics Faculty, Taras Shevchenko National University.
Spectral features of luminescent emission of the Yb3+
, Eu3+
, Pr3+
ions were investigated. Two
types of emission centers formed by the RE ions in the tungstate lattices were observed by the
obtained spectra. Site symmetry and crystal field stretch action were analyzed for the both
types of centers on example of the PbWO4-Eu3+
crystals. Structures of these centers were
discussed and different types of incorporation of the impurity RE ions in the lead tungstate
lattice (RE ions at Pb or W sites) for the observed two types of centers were shown. The
assumption was made about effects of defect structure of matrix on spectral properties of the
first type of centers that allows some authors to find six types of centers in these crystals [3].
The influence of the impurity RE ions on relative concentrations of various types of defects in
the host matrices is considered. The conclusion is made about formation of additional RE-
induced channel of creation of excitons responsible for the blue emission band in the PbWO4
crystals.
[1] Basiev, T.T., Baumer, V.N., Gorobets, et. al., Crystallography Reports (2009) 54, 697-
701.
[2] Li, W., Huang, H., Feng, X., Phys. Stat. Sol. (a) (2005) 202, 2531-2536.
[3] Huang, Y., Seo, H.J., J. Phys. Chem. A (2009)113, 5317-5323.
135
PI_27 Dependence of Luminescent Properties of Rare Earth Ions Incorporated
in Vanadate Matrices on Ways of Charge Compensation
S.G. Nedilko
1), O.V. Chukova
1), V.P. Scherbatsky
1), V.P. Sheludko
2), S.V. Virko
3)
1)
Physics Faculty, Taras Shevchenko National University of Kyiv, 4-b, acad. Hlushkov Ave.,
03680, Kyiv, Ukraine 2)
Olexander Dovzhenko Glukhiv State Pedagogical University, Glukhiv, Ukraine 3)
Institute of Semiconductor Physics, NAS of Ukraine, 45, Nauki Ave, 03680 Kyiv, Ukraine
E-mail: [email protected]
Vanadate compounds are perspective for a wide range of applications: from optoelectronics to
medicine. In particular, light emitting materials based on rare earth orthovanadates are widely
used for various science and technology purposes. Search of new materials with improved
spectral characteristics for certain applications is always an actual task of material science.
Properties of the RE ions luminescence depend on their arrangement in the host matrix, e.g.
site symmetry and crystal field stretch. We have carried out spectral luminescent investigation
of two different types of vanadate compounds doped with rare earth ions. There are LaVO4
and Ca5(VO4)3OH matrices. The both compounds contain the VO43-
anions, but different
types of cations. The LaVO4 composition allows replacement of the La ions with other RE
ions. The Ca5(VO4)3OH composition requires charge compensation.
The La1-xRExVO4 powders were synthesized at 680 C by solid state reaction or co-
precipitation methods [1]. Phase compositions and crystal lattice parameters were determined
by XRD. The LaVO4 samples possess monoclinic structure, whereas the La1-xRExVO4
compositions transform in tetragonal structure at x > 0.1. The Ca5(VO4)3OH compounds were
obtained from aqueous solutions of corresponding compounds by thermolysis at 550 - 600 C
and sintering at 700 C [2]. The RE3+
dopants were accompanied with the M+ (Li, Na, K, Cs)
iones. XRD analysis confirms substitution of Ca2+
cations with M+ and RE
3+ pairs up to x =
0.4.
Spectra of the La1-xRExVO4 compounds reveal one type of the RE emission centers. We
have found some differences in luminescence and excitation spectra of samples obtained by
different methods. These differences are explained by changes of lattice structure with rise of
impurity concentration and size effects caused by increasing of role of surfaces of particles
under decreasing of their sizes. Spectral luminescent investigation of the Ca5(VO4)3OH
compounds reveals two types of emission centers formed by the RE ions with different
arrangement in the crystal lattice. Efficiency of excitation energy transfer from matrix to the
RE emission centers was compared for different types of compositions. The direct La – RE
substitution gives a higher efficiency of energy transfer from matrix to the RE ions. This leads
to total quenching of matrix emission caused by electron transitions in the VO43-
anions,
whereas for the Ca5(VO4)3OH structure allows to observe at the same time the RE and matrix
emission. The investigation was supported by DFFD of Ukraine (Project # F54/040).
[1] O. Chukova, S.G. Nedilko, S.A. Nedilko, V. Scherbatsky, T. Voitenko, Solid State
Phenomena, 2013, 200, 186-192.
[2] L.I. Ardanova, O.V. Chukova, E.I. Getman, V.I. Marchenko, S.G. Nedilko, V.P.
Scherbatsky, Functional Materials, 2002, 9, 326-331.
136
PI_28 Study of photoluminescence polarization of organic crystals
T. Prutskij1)
, M. J. Percino1)
, T. Perova2)
1)
Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Privada 17 Norte, No
3417, col. San Miguel Hueyotlipan, 72050, Puebla, Pue., México 2)
Department of Electronic and Electrical Engineering, University of Dublin, Trinity College,
Dublin 2, Ireland
E-mail: [email protected]
Single organic crystals have a long-range structural ordering and frequently exhibit an optical
anisotropy. The analysis of the photoluminescence (PL) emission polarization helps to reveal
the correlation between the molecular packing and the optical properties and clarifies the
nature of electronic transitions within the crystalline structure.
Organic crystals formed by aromatic amines now are finding increasingly their usage in
optoelectronics as materials for holes transport in nano-devices. In particular triphenylamine
and its derivatives are well-known hole-transport solid-state electroluminescent materials for
photovoltaic applications that have a high luminescent efficiency.
Here we measured and analyzed the PL emission from the organic crystals consisting of (Z)-
3-(4-(diphenylamino)phenyl)-2-(pyridin-2-yl)-acrylonitrile (DPPyACN) molecules and grown
as long crystals with the thickness of approximately 100 µm.
The PL emission of DPPyACN was studied both in solutions and in solid crystals. The PL
emission of these crystals excited at 515 nm has three PL bands with different angular
polarization dependencies, being polarized towards the direction perpendicular to the crystal
long axis orientation (see Fig.1). The spectral position of one of these bands is the same as the
PL emission of the DPPyAC molecule in dilute solutions in different “poor” solvents.
Supposing that each one of the peaks of the emission spectrum corresponds to certain inter-
and intra- molecular π- π conjugation, the different angular dependencies points out to the
different orientations of these bonds inside of the crystal.
Fig. 1 a) PL emission spectra for two orthogonal polarizations, b) polarization angular dependencies
for different spectral PL bands.
We also compare the PL emission polarization with the polarization of the Raman spectrum,
finding that the Raman scattering polarization is consistent with the PL polarization.
137
PI_29 A glow of OH and OD radicals upon mechanical destruction of the hydrated
terbium and cerium sulfates in argon medium
A. A. Tukhbatullin, M. R. Muftakhutdinov, A. M. Abdrakhmanov, G. L. Sharipov
Institute of Petrochemistry and Catalysis RAS, 450075, 141, pr. Oktyabrya, Ufa, Russia
E-mail: [email protected]
Triboluminescence (TL) is a glow that occurs upon crystals destruction, first described
in 1605 [1]., A role of the products of mechanochemical reactions in TL have been unclear for
a long time, though a chemical activity of surfaces renewed by the crystals destruction was
postulated [2]. There are no articles on the spectral evidence of mechanochemical reactions
whose products are TL emitters.
We report the registration of a glow of OH and OD radicals which are products of the
destruction of the crystallization water (H2O and D2O). The latter is formed during the
destruction of the crystalline hydrate lanthanide salts. Filling the working cell by argon when
the TL of crystals Tb2(SO4)3∙8H2O and Ce2(SO4)3∙8H2O was occurring, the lines of argon and
OH radical were also observed in the glow of the gas TL component together with a solid one
(the lines of terbium and cerium ions in the emission spectrum), in addition to the nitrogen
lines in the UV region. On the basis of simple experiments (in particular, freezing out the
water vapor contained in argon) we has proved that glow of OH radical is not associated with
the atmosphere water vapor. As suggested, the source of OH radical is the crystal water,
decomposing with the mechanical effect on the hydrated terbium and cerium sulfates. The
most informative way to verify the hypothesis is a replacement of the crystal H2O by D2O and
subsequent comparison of the TL spectra. Replacement of H2O by D2O in crystals
Tb2(SO4)3∙8H2O was carried out in two stages.
In the first step the crystals were kept in a muffle furnace at T = 250 ºC. At the
temperature, the complete dehydration of Tb2(SO4)3 • 8H2O crystals occurs. The content of
crystallized water was estimated by lifetime τ (i.e. the mean duration) of terbium sulfate
photoluminescence. For anhydrous Tb2(SO4)3 salt, τ = 2500 μs. At the second stage, D2O was
gradually added to the dehydrated crystals.
Replacement of H2O by D2O in terbium sulfate crystals affected the TL gas component.
Thus, in the deuterated crystals when Ar blowing at 1.3 atm pressure, the glow of OD radical
was observed in the spectrum. When considering the TL spectra of Tb2(SO4)3∙8H2O and
Tb2(SO4)3∙8D2O in the range of 275 - 320 nm, their similarity is obvious. However, the
characteristic differences are also noticeable. For example, in the transition range of 1-0 bands
A2Σ+ → X2Π OH, in the case of the deutarated crystal there is a shift of the maxima towards
the higher values of wavelengths that are characteristic for the OD radical. In addition, the
intensity of the bands A2Σ+ → X2Π of the deuterated crystal in the TL spectrum is twice
higher than in the case of H2O.
[1] Harvey E.N. A History of Luminescence from Earliest Time until 1900. –
Philadelphia: Amer. Phil., Soc., 1957. – 432 p.
[2] N.A. Krotova, Vestn. Akad. Nauk SSSR. 1970. V. 40 No. 12. P. 34.
138
PI_30 Energy transfer kinetic in nanocrystals doped with rare earth
and transition metal ions
Glushkov N. A.
Laser Materials and Technology Research Center at Prokhorov General Physics Institute,
RAS, 119991, Vavilov Str. 38, Moscow, Russia
The donor excitations static quenching by ensemble of randomly distributed acceptors was
earlier investigated by us in terms of the sample consisting of spherical nanocrystals doped
with rare earth and transition metal ions [1-4]. The donor-donor excitation jumps were also
earlier taken into account in our work [5]. In this work the donor excitations ultrafast
quenching by ensemble of randomly distributed acceptors was considered in terms of the
sample consisting of spherical nanocrystals doped with rare earth and transition metal ions.
In common case, migration both accelerates excitation quenching process and defines
functional dependence of quenching kinetic on the basic system parameters such as donor (cD)
and acceptor (cA) concentrations, donor-donor (CDD) and donor-acceptor (CDA) transfer
efficiency microparameters, and donor-donor (SD) and donor-acceptor (SA) energy transfer
multipolarity. As a result, the problem related to basic parameters definition is very important
for laser spectroscopy.
While carrying out the investigations we used an analytical approach and approach based on
numerical Monte-Carlo simulation to reveal the functional kinetic dependences under
condition the donors are excited with a short impulse. The current investigation showed that
the stacionary migration-accelerated quenching stage may be missing on the kinetic of
migration-accelerated quenching in the sample consisting of spherical nanocrystals doped
with rare earth and transition metal ions but quenching kinetic has multistage character. The
revealed effect is important not only from theoretical standpoint, but it is also has an
important applied meaning. Namely, for wide number of systems starting with strong donor-
donor interaction systems (CDD/CDA >> 1) and ending with strong donor-acceptor interaction
systems (CDD/CDA << 1) by means of varying the donor and acceptor concentrations it
became possible to reduce the functional kinetic behavior to ferster-like dependences. This in
its turn allows to define the single-valued basic definitions of energy transfer process
parameters.
This work is supported by:
RFBR (grant 12-02-31447 мол_а)
Programme of Presidium RAS 24П “Fundamental grounds for technologies,
nanostructures and nanomaterials”
* RFBR (grant 11-02-00248 а)
[1] N. A. Glushkov, T. T. Basiev, Yu. V. Orlovskii; “Kinetics of the Direct Energy
Transfer of Optical Excitation in Crystalline Nanoparticles: Theory and Monte Carlo
Computer Simulation”, Russian nanotechnologies 4, 9-10, 152 (2009)
[2] T. T. Basiev, N. A. Glushkov, “ Förster-like nonexponential energy transfer kinetics in
doped nanoparticles”, Opt. Mater. 32, 12 (2010) 1642
[3] T. T. Basiev, I. T. Basieva, N. A. Glushkov, “Theoretical analysis of the static
quenching of optical excitations in luminescent nanoparticles”, JETP Lett. 91, 5
(2010), 254
[4] T.T. Basiev, I.T. Basieva, N.A. Glushkov, “Two- and three-dimensional restricted
geometry case of luminescence quenching”, J. Luminescence, 130 (2010) 2305
[5] N. A. Glushkov, T. T. Basiev, I. T. Basieva, “Ultrafast migration-accelerated
quenching kinetic in nanoparticles”, JETP Lett. 93, 12 (2011), 777
139
PI_31 Energy transfer in dye-doped nanoparticles from Ln3+
complexes
L. Yu. Mironov, E. B. Sveshnikova, V. L. Ermolaev.
NRU ITMO, 197101, Saint-Petersburg, Russia
E-mail: [email protected]
We have studied energy transfer of electron excitation in nanoparticles (NP) formed
from Ln3+
complexes with β-diketones in aqueous solutions. It was shown previously that
these NP capture dye molecules from solution in process of their formation and efficiently
sensitize dye fluorescence via S–S energy migration through ligands of complexes and energy
transfer to dye molecules [1]. The dependence of energy transfer efficiency to dyes
incorporated in NP’s on choice of Ln3+
ions absorbing in the region of fluorescence of organic
ligand complexes was examined. It was shown that τfl of complexes with La3+
, Lu3+
and Gd3+
ions were hundred times less (several ps) than τfl of the same Al complexes. Such decrease of
τfl indicates the enhancement of intersystem crossing due to high electron shells overlapping
between Ln3+
ions and β-diketones. It was shown that presence of dye molecules with S1
energy levels lower than S1 energy levels of ligands in NP’s from complexes of any Ln3+
ions
resulted in appearance of the sensitized fluorescence of dye molecules. However when excited
states of Ln3+
ions are lower than S1 level of ligands there is competition between energy
transfer to dye molecules and Ln3+
ions. Sensitized fluorescence intensity of rhodamine 6G is
similar in NP’s from complexes of La3+
, Eu3+
, Sm3+
ions and τfl of La3+
, Lu3+
complexes are
equal to 2-3 ps. It means that energy transfer probability (ktr) from S1–level of complexes to
Eu3+
and Sm3+
ions is considerably less than 5·1011
s-1
. However in NP’s from Nd3+
, Pr3+
,
Ho3+
, Tm3+
and Er3+
complexes sensitized fluorescence intensity is more than ten times less
than in NP’s from La3+
complexes. The dependence of fluorescence of dye molecules
incorporated in these NP’s (excited in absorption band of complexes and in own absorption
band of dye molecules) and Ln3+
ions choice was studied. This examination allowed us to
evaluate ktr value for energy transfer from complexes S1–level to Ln3+
ions. It was shown that
ktr values were equal to 1013
s-1
, 5·1012
s-1
and 2·1012
s-1
for Nd3+
, Er3+
and Pr3+
complexes
respectively. Therefore, energy transfer probabilities from ligands S1–level to these ions are
similar to limiting value estimated for S1-levels energy migration in aromatic compounds.
Great electron shells overlapping of Ln3+
ions with ligands of complexes and high ktr
magnitudes only for ions that have spin-allowed transitions in the region of spectrum overlap
of complexes and ions led us to the conclusion that the exchange mechanism of energy
transfer from ligand S1–level to Ln3+
ions in these Ln diketonates takes place. This is the main
difference from earlier observed inductive resonance energy transfer from organic molecules
S1–level to Ln3+
ions [2, 3].
The investigation of energy transfer mechanism in dye-doped NP from Ln3+
complexes with β-diketones is of great interest because it allows to lower detection limit of
fluorescent dyes in aqueous solutions and to create brightly fluorescent nanoparticles as labels
in biology and medicine. We thank Russian Foundation of Basic Research (project no. 13-03-
00252-A) for supporting this work.
[1] V.L.Ermolaev, E.B.Sveshnikova, Russ. Chem. Rev. V. 81, No 9, P. 869-889 (2012)
[2] T.A. Shakhverdov. In: Excited Molecules. Transformation Kinetics. Nauka.
Leningrad. 1982. P.75-88. (In Russian).
[3] G.A. Hebbink, S.I. Klink, L. Grave, P.G.B.O. Alink, F.C.J.M. van Veggel.
ChemPhysChem. V. 3, P. 1014 (2002).
140
PI_32 Erbium doped SrTiO3 crystals: optical spectroscopy
A.P. Skvortsov1)
, N.K. Poletaev1)
, Z .Potucek2)
, L. Jastrabik2)
, A. Dejneka2)
and
V.A.Trepakov1,2)
1
Ioffe Physical-Technical Institute RAS, 194 021, Politekhnicheskaya 26, Saint-Petersburg,
Russia 2 Institute of Physics AS CR, Na Slovance 2, 182 21 Praha 8, Czech Republic
E-mail: [email protected]
Strontium titanate SrTiO3 is a well known prominent representative model of
perovskite-type highly polarized oxides, whose attractive functional properties appreciable
depend on the impurities and defects. Therefore, knowledge about structure and microscopic
properties of active impurity centers in SrTiO3 are certainly of considerable importance.
In this work we focused on studies of f-f optical absorption and photoluminescence
spectra of Er3+
impurity centers in strontium titanate. Single crystals of SrTiO3 with 50 ppm
of Er3+
in the charge have been grown by the Verneuil method. The absorption spectra were
recorder at 293, 77 and 2 K within 370 – 700 nm of the spectral region. The pronounced
structured spectra of intraconfigurational optical transitions from the 4I15/2 ground state to
excited levels of Er3+
ions were observed. At T = 2 K detail studies of the optical transitions to
the 4F9/2,
4S3/2,
2H11/2,
2H9/2 excited levels allowed us to determine quantity of components for
the individual transitions. Optical emission spectra of the 4S3/2,
4F9/2→
4I15/2 transitions were
excited by a He-Cd laser (325 nm) and studied in the temperature region 1070 К. The detail
investigations at T = 10 К provides information about number of energy levels of 4I15/2
ground and the first excited 4I13/2 states.
The number of spectral lines observed at low temperatures was found exactly
corresponds to that theoretically possible for f-f electron transitions of Er3+
ions in non-cubic
crystal field in accordance with tetragonal symmetry of SrTiO3 crystals below the temperature
of the antiferrodistorsive structural phase transition taking place at ~105 K.
Thus, the detail analysis of the absorption and luminescence spectra allowed us to
determine energies of the excited states levels and energy structure of the ground 4I15/2 state for
the Er3+
dominant centers of non-cubic symmetry.
The point symmetry of Er3+
centers, their position in the crystal lattice and related
charge compensation mechanisms are discussed.
141
PI_33 Study of absorption spectra of Li6Y(BO3)3:Er3+
crystals
Á. Péter1)
, K. Polgár1)
, N. Poletaev2)
, A. Skvortsov2)
1
Institute for Solid State Physics and Optics, Wigner Research Centre for Physics of HAS,
Konkoly-Thege M. 29-33, Budapest, Hungary 2 Ioffe Physical-Technical Institute RAS, 194 021, Politekhnicheskaya 26, Saint-Petersburg,
Russia
Li6Y(BO3)3 (LYB) crystals are of great interest because they are efficient scintillators
for sensitive detectors of ionizing radiation and thermal neutrons. Moreover this crystals
activated with rare earth impurities is a promising laser medium.
LYB single crystals doped with Er3+
( ~0.03 % wt in the charge) were grown by the
Czochralski method in platinum crucibles in air.
The optical absorption spectra of LYB:Er3+
have been studied at 293, 77 and 2 K within
370 – 700 nm of the spectral region. The absorption lines corresponding to
intraconfigurational optical transitions from the 4I15/2 ground state to the excited levels of Er
3+
ions were observed. At T = 2 K detail investigations of the optical transitions to the 4F9/2,
4S3/2,
2H11/2,
4F7/2,
4F5/2,
4F3/2,
2H9/2 and
4G11/2 excited levels allowed us to determine quantity of
components for the individual transitions. The number of spectral lines observed at 2 K was
found exactly corresponds to that theoretically expected for f-f electron transitions in Er3+
ions
occurring in non-cubic crystal field in accordance with monoclinic symmetry of Li6Y(BO3)3
crystals.
The detail analysis of the absorption spectra obtained allowed one to determine energies
of Stark sublevels of the states under study.
Thus, the number of the spectral lines observed at 2 K and their narrowness indicate
convincingly that the Er3+
impurities ions occupy one regular position in the LYB crystal
lattice. The Y3+
position appears to be most likely.
This work was supported by the Grants OTKA CK –80896 and OTKA K –83390
and the Program of Interacademic Cooperation between the Russian Academy of Sciences and
the Hungarian Academy of Sciences.
142
PI_34 Synthesis, crystal structure and luminescence properties
of CaY2Ge3O10:Ln3+
, Ln = Eu, Tb
O.A. Tarasova, L.L. Surat, M.A. Melkozerova, A.P. Tyutyunnik, I.I. Leonidov, V.G. Zubkov
Institute of Solid State Chemistry, UB RAS, 620990, Ekaterinburg, Russia
E-mail: [email protected]
CaY2Ge3O10, a new optical host reported recently [1], belongs to a group of germanate-based
luminescent materials that have received much attention for potential use in field emission
display applications and thin film electroluminescent devices [2]. Lanthanide-doped
germanates have been extensively studied as promising laser systems [3, 4] as well as
phosphors for up- and down-conversion [5, 6]. Superior chemical and thermal stability, the
lack of moisture sensitivity and relatively simple processing are the advantages offered by this
group of oxides.
In this report, we consider luminescence in CaY2Ge3O10:Ln3+
, Ln = Eu, Tb, prepared by a
synthesis route via EDTA-complexing process and by a conventional solid-state reaction.
Powder XRD study of CaY2-xRxGe3O10 (R = Eu or Tb; x = 0.1-1.0, 2.0; ∆x = 0.1) shows that
the solid solutions crystallize in the monoclinic system with the space group P21/c, Z = 4. The
crystallinity and particle size of the as-prepared samples increase with calcination temperature
rise that leads to the growing emission intensities. The photoluminescence spectra of
CaY2Ge3O10:Tb3+
consist of several intense peaks in the green spectral range, which
correspond to the characteristic transitions 5D4 →
7FJ, the
5D4→
7F5 emission at ~542 nm is
the strongest. A substantial luminescence contribution is observed from the higher emitting
levels 5D3→
7FJ in blue and near UV ranges. The intensity ratio between emissions from
5D3
and 5D4 levels varies significantly with concentration of Tb
3+ ions in the lattice and with the
preparation temperature. The CaY2Ge3O10:Eu3+
phosphors emit light in the red spectral range.
Appropriate CIE chromaticity coordinates for CaY1.7Eu0.3Ge3O10 are x = 0.54 and y = 0.29.
The excitation under 250 nm (Eu–O CTB) is more efficient for the samples prepared using
synthesis via EDTA-complexing process, while the samples obtained by the solid-state
reaction demonstrate higher emission intensity under excitation at λex = 393 nm. This
observation suggests a favorable opportunity for a potential LED application of the obtained
phosphors under UV diode-chip excitation operating at different wavelengths in the 250–400
nm range.
This work was supported by RFBR (grant No. 13–03–00047a) and UB RAS (grant Nos.
12–P–3–1003, 12–T–3–1009, 13–3–NP–686).
[1] H. Yamane, R. Tanimura, T. Yamada, J. Takahashi, T. Kajiwara, M. Shimada, J. Solid
State Chem. 179 (2006) 289–295.
[2] F. Zhao, P.M. Guo, G.B. Li, F.H. Liao, S.J. Tian, X.P. Jing, Mater. Res. Bull. 38 (2003)
931–940.
[3] A.A. Kaminskii, E.L. Belokoneva, B.V. Mill, Yu.V. Pisarevskii, S.E. Sarkisov,
I.M. Silvestrova, A.V. Butashin, G.G. Khodzhabagyan, Phys. Status Solidi (a) 86 (1984)
345–362.
[4] J.J. Romero, D. Jaque, F. Ramos-Lara, G. Boulon, Y. Guyot, U. Caldiño, J. GarcíaSolé,
J. Appl. Phys. 91 (2002) 1754.
[5] F. Ramos-Lara, D. Jaque, J García-Solé, U. Caldiño G., J. Phys.: Condens. Matter
12 (2000) L441–L449.
[6] G.J. Gao, L. Wondraczek, J. Mater. Chem. C 1 (2013) 1952–1958.
143
PI_35 Dependences of optical spectra of UV irradiated crystals Na4Y6F22:Ce3+
,
Na4Y6F22:Ce3+
,RE3+
(RE3+
: Yb3+
, Eu3+
) versus temperature
D.I. Tselischev, A.K. Naumov, E.Yu. Tselischeva, S.L. Korableva
Kazan Federal University,420008, Kremlevskaya 18, Kazan, Russia
Investigations of recent years shown that in most fluoride crystals doped by Ce3+
ions after
UV irradiation color centers (CC) formation occurs. This process often completely suppresses
gain in crystals that might be used as active media. In previous works [1,2,3] it has been
shown that Yb3+
ions in Ce-activated crystals effectively suppress color centers formation
process.
In this paper we present the results of studies of optical properties of Na0.4Y0.6F2.2:Ce3+
Na0.4Y0.6F2.2:Ce3+
,Yb3+
, Na0.4Y0.6F2.2:Ce3+
,Eu3+
crystals after UV irradiation by 4ω0 of
YAG:Nd laser. Appearance of additional absorption bands in all the samples after UV
irradiation was observed. In crystal Na0.4Y0.6F2.2:Ce3+
additional bands change over time.
These bands associated with absorption of CC. In case of Na0.4Y0.6F2.2:Ce3+
crystal co-doped
by Eu3+
or Yb3+
ions these changeable bands were not observed after UV irradiation. As a
result it was concluded that Yb3+
and Eu3+
ions in the Na0.4Y0.6F2.2:Ce3+
crystal inhibit the
formation of CC which are formed after UV exposure.
To explain this fact it was necessary to estimate positions of the ground state of CCs and the
ground states of Ce, Yb, Eu ions relatively the valence and conduction bands of the crystal
Na0.4Y0.6F2.2. For this purpose optical spectra of the crystals Na0.4Y0.6F2.2:Ce3+
,
Na0.4Y0.6F2.2:Ce3+
,Yb3+
and Na0.4Y0.6F2.2:Ce3+
,Eu3+
were measured at various temperature in
range 300 – 750 K. After analyzing experimental data it was concluded that in the crystal
Na0.4Y0.6F2.2:Ce3+
two types of CC are presented. Activation energy of these CC were
estimated. The positions of ground states of Yb and Eu ions in bivalent state were defined.
Using these data positions of ground states of the other rare earth (RE) ions in bivalent and
trivalent state were calculated.
As a result of this study the energy levels diagram were constructed for CCs and RE ions in
crystal Na4Y6F22.
[1] A.K.Naumov et al. “Spectral-kinetic and photochemical properties of
Ce3+
:Na4Y6-xYbxF22 single crystals” SPIE, IRQO’03 - V.5402. P.430-437 (2004)
[2] E.Yu. Koryakina et al. “Spectroscopic properties of color centers in crystal KY3F10: Ce3+
co-doped by Yb3+
ions” in Proc. XIV Feofilov Symposium, P.We-P-57 (2010)
[3] D.I. Tselischev et al. “The formation of stable divalent state of Yb ions in the crystal
Na4Y6F22: Ce3+
, Yb3+
after action of intensive UV irradiation”, Optics and Spectroscopy,
vol. 111, 3, P. 415-419 (2011)
144
PI_36 The effect of the magnetic field strength and excitation intensity
on the shape of micro-photoluminescence spectra of MQW structures
on the InGaN/GaN base doped with Eu, Sm and Eu+Sm
M. M. Mezdrogina1)
, M. V. Eremenko1)
, E. I. Terukov1)
, Yu.V. Kozhanova2)
, O. V. Koplak3)
,
A.J. Dmitriev3)
1)
Ioffe Physiko-Technical Institute, 194021, Saint-Petersburg, Polytechnicheskaya 26, Russia 2)
S-PbSPU, Saint-Petersburg, 194021, Saint-Petersburg, Polytechnicheskaya 29, Russia 3)
Institute of Problems of Chemical Physics, Chernogolovka, Russia
E-mail: [email protected]
The effect of the magnetic field strength and excitation power on the micro-
photoluminescence (μ-PL) spectra of the undoped and doped with Eu, Sm and Eu+Sm
InGaN/GaN MQW structures has been investigated [1]. Diffusion technique was used for
doping with these impurities. Magnetic field in Faraday geometry in the range of 0-5 T was
provided by superconducting solenoid. The upper limit of impurity concentrations as was
determined by x-ray fluorescence technique was around 5·1018
cm-3
. For the determination of
the charge states of Eu and Sm Messbauer spectroscopy was used.
In the Eu-doped InGaN/GaN structures the decrease of their PL intensity with increase
of magnetic field strength at high optical excitation level (3,52·1023
photon·s/cm2), the greater
changes compare to those in undoped structures were observed: considerable decrease of the
PL intensity in the short range of μ-PL spectrum while only minor changes were recorded in
the long wave range region.
Sm as well as Eu is Van-Vleck paramagnetic impurity. The effects of Sm impurity on
the μ-PL spectrum of InGaN/GaN structures are differed compare to those of Eu under the
same conditions: PL intensity increases with increase of magnetic field, which is accompanied
by the blue-shift of λmax by approximately 0.8 nm. Increase of both the magnetic field strength
and excitation intensity results in the appearance of two PL bands in short-wave region of PL
spectra (λ= 425 nm and 430 nm).
Simultaneous doping with Eu and Sm leads to the changes in the short-range (434 nm
< λ < 460 nm) of the PL spectra: three PL bands of different intensity appear Also several PL
bands of smaller intensity are recorded in the long-wave region (735 nm<λ<800 nm) of PL
spectra The increase of the strength of magnetic field leads to only minor decrease of PL
intensity in the short-wave range region, leaving both spectral position and PL intensity of PL
lines in the long-wave region unchanged.
According to the data of Messbauer spectroscopy the main charge state in InGaN/GaN
structures doped with Eu is Eu3+
though smaller concentration of Eu2+
is also present.
As to Sm, only charge state 3+ (absence of 2+ state) was revealed in Messbauer
spectra. This circumstance is the suggested reason to observe essentially different effects of
doping of the studied InGaN/GaN structures with Eu and Sm on their μ-PL spectra.
Magnetic properties these structures with MQW on the base InGaN-GaN doped with Sm,
Eu+Sm were investigated by SQUID magnetometer. Temperature independent
paramagnetism as well as Curie like contribution to the temperature dependence of the
magnetization were observed in Sm,Eu and Sm+Eu doped samples. Field dependence of the
magnetization obeys Brilloin function typical for paramagnetic ions.
[1] M. M. Mezdrogina, E. S. Moskalenko, Ju. V. Kozhanova, Phys.Solid State, 53(8), 1680
(2011)
145
PI_37 Intensity of luminescence in visible and infrared spectrum range
in heterostructures n-Si/p-SiGe fabricated by direct wafer bonding
with simultaneous Er and Eu doping
M.M. Mezdrogina, R.V. Kuzmin, M. V. Eremenko, L.S. Kostina, E. I. Beliakova
Ioffe Physiko-Technical Institute, 194021, Saint-Petersburg, Polytechnicheskaya 26, Russia
The main problem of silicon photonics is the realization of stimulated irradiation in
near IR-region where optic losses in fiber-optic communication lines are minimal. It was
shown earlier [1] that silicon direct bonding with simultaneous rare-earth impurities doping is
promising for the design of n-Si/p-Si – devices in which stimulated irradiation on the
wavelength λ=1,54µm can be realized for light-emitted junction I13/2 – 4
I15/2 of Er3+
ion. In
this case rare-earth ion can be considered as an optic probe, which characterizes a space
dopant distribution.
In this paper, photoluminescence spectra of Si/SiGe-structures fabricated by direct
bonding (DB) are investigated. These structures seem to be prospected due to their specific
physical properties i.e. lower bandgap of SiGe-region and higher carrier mobility in it.
Bandgap lowering provides an additional opportunity for stimulated irradiation realization
due to excitation transfer from semiconductor matrix to rare-earth ion via resonance
mechanism whose action probability increases under these conditions.
We studied n-Si/p-SiGe structures produced by the DB technology. The resistivity of
float zone (111) silicon wafers was v=4; 40; 60 cm; Czochralski-grown (111) SiGe –
wafers with a resistivity of 40 cm had germanium concentration in the range of (4.1÷5.6)
wt. %. Before bonding, the mirror-polished wafers were subjected to standard RCA-rinsing
and hydrophilization. The wafers were brought into contact in (0.1 – 1)wt % de-ionized water
(v=18 MΩcm) solutions of EuCl3 or ErCl3 which served as a source of Eu or Er diffusion
during the further high-temperature processing of the bonded wafers. They were annealed in
air at 95°C for 2 h and at 1250°C for 5 h. Such a method of impurity introduction provides a
wide range of its concentration in Si/SiGe – structures.
Photoluminescence spectra measurements were performed at diffraction spectrometer
СДЛ-2 with reverse linear dispersion 1.3 nm/mm in the region of edge and extrinsic
luminescence of samples under investigation. Spectral resolution at spectrum recording was
2.6Å
Spectra of n-Si<Er,Eu>p-SiGe - structures with different Er and Eu concentration as
well as with different Ge content in SiGe-layer were investigated. It was revealed that at
Т=77К, radiation lines attributable to the recombination of free excitons as well as to excitons
fixed at the neutral donor dominated in photoluminescence spectra of n-Si<Er>p-SiGe -
structure (n-Si with v=60 cm and p-Si/Ge with 5,6 wt.% Ge) doped from 0,2% Er water
solution.
For the realization of radiation that is specific for the interior-on-centre transition 4I13/2–
4I15/2 of Er
3+ ion and
5D0 -
7F1 of Eu
3+ ion, the Er, Eu concentration optimization in n-
Si/p-SiGe-compositions with Ge content (4,1÷5,6) wt.% in SiGe-layer was performed.
[1] M.M. Mezdrogina et.al. Proc. of “Silicon’2012”. Book of abstracts. P. 179.
146
PI_38 Spectral-kinetic properties of Nd3+
ions doped series of Li Y1-xLuxF4 (x=0 – 1)
mixture crystals
A. K. Naumov, R. D. Aglyamov, D. I. Tselischev, E. Yu. Tselischeva, M. A. Marisov,
A. S. Nizamutdinov, V. V. Semashko, A. V. Lovchev, O. A. Morozov, V. N. Efimov,
S. L. Korableva
Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russia
In 2002 year LiYxLu1-xF4 (x=50, 75, 100 mol %) the mixture crystals doped with neodymium
were successfully grown by the Czochralski technique in CF4 atmosphere by Ranieri with
coauthors [1]. As it was shown in the paper, optical quality of grown crystals ever better then
one of main crystals their constituents base, with low cost of the materials. In work [2] the
series of six crystals samples LiY1-xLuxF4 (x=0 – 1), all of it activated by 1% of Nd3+
ions, has
been grown by Bridgman technique. This series of the samples have been studied by optical
spectroscopy and EPR methods and the anomaly high distribution coefficient of activator
(about 1.5-2 higher than for YLF and LiLuF4 crystals) has been founded in the sample where
“x” was about 0.2 (see fig. 1). It must be note that this sample didn`t lost their optical quality.
Fig.1 The integral absorption coefficients of Nd3+ ions in crystal samples LiY1-xLuxF4:Nd3+(1%)
for two polarizations versus X. Integration was performed in 700 to 900 nm spectral range
In this work the results of optical spectroscopy methods studies of the series of the crystals
samples: LiY1-xLuxF4 (x=0 – 1) activated by 1 at.% in the melt of Nd3+
ions will be presented.
The polarized absorption spectra, the polarized luminescence spectra together with
luminescence kinetic of the samples and analyze of this results will be submitted. The
perspective of using this material as active media for diode pumping lasers will be discussed.
[1] I.M. Ranieri, S.P. Morato, A.H.A. Bressiani et. al., J. Alloys Compnds. 344 (2002) 203
[2] Russian patent 2367731, method of increasing the distribution coefficient of rare-
earth ions in crystals of cerium subgroup double fluorides with scheelite structure
/V.V. Semashko, A.S. Nizamutdinov, A.K. Naumov, S.L. Korableva, V.N. Efimov//
The publication data: 27.05.2009
0.0 0.2 0.4 0.6 0.8 1.040
45
50
55
60
65
70
75
80
85
90
95
Inte
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l a
bso
rptio
n c
oe
ffic
ien
t, n
m*ñ
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"õ"LiYF4
LiLuF4
147
PI_39 Fluctuation kinetics of luminescence hopping quenching of Ce3+
5d level
in YPO4·0.8H2O nanocrystals
A.V. Popov1,2)
, Yu.V. Orlovskii1,2)
, A.S. Vanetsev1)
, O.M. Gaitko3)
, E.O. Orlovskaya2)
,
Ilmo Sildos1)
1)Institute of Physics, University of Tartu, 51014, 142 Riia str., Tartu, Estonia
2)General Physics Institute of RAS, 119991, 38 Vavilov str., Moscow, Russia
3)Chemistry Department of Moscow State University, 119992, 3 Leninskie Gory, Russia
We determine the kinetics of impurity quenching N(t) = I(t)/exp(-t/R) (R =33.6 ns) of the
lowest 5d1(21) level of Ce
3+ in the YPO4·0.8H2O nanocrystals at 300K. The fluorescence
quenching at the late stage of the kinetics is determined by two processes depending on Ce3+
concentration: static dipole-dipole quenching (Eqs. 1, 2 ) caused by the OH––group vibrations
dominating at 0.2at.% of Ce3+
, and Ce3+
–Ce3+
dipole-dipole energy migration with subsequent
Ce3+
–OH– quenching prevailing at 2.0 at.% of Ce
3+ (Fig.1), see [1]. In the latter sample we
observe for the first-time non-stationary kinetics of the impurity quenching of the donors level
whose spontaneous emission rate is determined by the allowed 5d – 4f dipole transitions. It
starts from static quenching within time interval t1 – ts (Eqs. 3, 6) and ends at t > tf with
fluctuation kinetics of luminescence hopping quenching Nf(t) ((Eq. 4) and (Eq. 7)) if
condition CDD >> CDA is fulfilled, see [2].
( ) ( √ ) ( ) ( )
( ); ⁄ ( )
( ) [( ) ⁄ ] [ ( )√ ] ( ) ⁄ ( ) ( ) ( ) ⁄ ( )
( )
⁄ ( ) ( )
( )
where A and D are the macroparameters of static energy transfer and energy migration from
initially excited donors. We estimated from experiment: A = 0.09 ns–1/2
at 0.2 at.% of Ce3+
,
0.24 ns-1/2
at 2.0 at.% of Ce3+
, and D = – A = 0.15 ns–1/2
, α = 0.6 (Eq. 5). The value of
microparameter CDA of Ce3+
–OH– energy transfer is 2.5 nm
6/ms, calculated from the ordered
stage of the kinetics (Eq. 3) at t1 = 52 ns and Rmin = 0.23 nm. The microparameter CDD for
Ce3+
– Ce3+
energy migration was obtained from Eq. (8): CDD = 7.1·103
nm6/ms (ND = 0.24
nm–3
) indicates that the condition of hopping quenching (CDD >> CDA) is fulfilled very well.
We found that NA=7.9 nm-3
calculated from Eq. (2) is in agreement with the water
concentration calculated from YPO4•0.8H2O chemical formula and the unit cell volume that
confirms the validity of the model. The fluctuation kinetics of hopping fluorescence
quenching starts earlier than that expected from the theory in the bulk crystal [2] due to the
limited geometry of nanocrystals.
t1/2
, ns1/2
0 2 4 6 8 10 12 14
ln(N(t))
-3
-2
-1
0
1
2
t1
Figure 1. The impurity quenching kinetics ln(N(t)) vs t1/2
of the 5d1(21) level of Ce3+ in the YPO4·0.8H2O
nanoparticles at 300K depending on Ce3+ concentration:
0.2 at.% Ce3+ – broken line, 2.0 at.% Ce3+ – dotted line, Curves 1 and 2 are the fitting lines. The
A= 0.09 ns–1/2 and = D + A 0.24 ns-1/2
macroparameters are determined from the slope
of the curves 1 and 2, respectively;exc=266 nm,
det=380 nm.
European Social Fund (Gr. #MTT50, MJD167) and RFBR #11-02-0248 support our work.
[1] T. Forster. Ann. Phys. 2 (1948), p. 53
[2] S. G. Fedorenko, A. I. Burshtein, A. A. Kipriyanov. Phys. Rev. B, 48 (1993), 7020
148
PI_40 Spectroscopy of the 5d1-4f
1 transitions of Ce
3+ in yttrium phosphate nanocrystals
A.V. Popov1,2)
, Yu.V. Orlovskii1,2)
, C.-G. Ma1,3)
, A.S. Vanetsev1)
,
O.M. Gaitko4)
, E.O. Orlovskaya2)
, S.Lange1)
, Ilmo Sildos1)
1)Institute of Physics, University of Tartu, 51014, 142 Riia str., Tartu, Estonia
2)General Physics Institute of RAS, 119991, 38 Vavilov str., Moscow, Russia
3)College of Mathematics and Physics, Chongqing University of Posts and
Telecommunications, 400065, 2 Chongwen Road, Chongqing, P.R. China 4)
Chemistry Department of Moscow State University, 119992, 3 Leninskie Gory, Russia
We measure and model for the first-time the crystal-field splitting (CFS) for the Ce3+
in 5d1
configuration in the hexagonal rhabdophane-type YPO4·0.8H2O:Ce3+
nanocrystals (NCs) (the
hexagonal D2 optical center of Ce3+
), which fit each other (Table, columns 1–3). For
modelling we use the exchange charge model of CF theory [1]. The CFS of the D2 center is
found to be about 1.5 times larger than the CFS of the tetragonal D2d optical center of Ce3+
in
the tetragonal xenotime-type YPO4:Ce3+
NCs (Table, columns 1 and 4 respectively). The later
have the same CFS as in the YPO4:Ce3+
bulk crystal [2].
The spontaneous emission decay time R(D2) from the lowest 5d1(
21) level at T=300 K is
33.6 ns found from the slope of the final stage of the fluorescence kinetics (Fig.1 a). The
kinetics at T=10 K is even longer. So, the latter is found to be more than as twice as long than
the spontaneous emission decay time for the D2d Ce3+
center in the YPO4 bulk crystal (or in
nanocrystals) (Fig. 1 b, curves 1 and 2 respectively). We believe that we measure the
spontaneous emission decay time, because deactivation of the level by the multiphonon
relaxation process is negligible, because the 4f1(2F7/2)–5d
1(
21) energy gap is too wide
(~30000 cm–1
) in comparison with the value of h(OH–) = 3600 cm
–1 and even more so with
h(PO42–
) = 1000 cm–1
.
Table. Measured (Exp.) and calculated (Calc.) CFS
of the 5d1 configuration of the D2 (YPO4·0.8H2O)
and D2d (YPO4) optical centers of Ce3+.
D2, cm–1 D2d, cm–1
1 2 3 4 5 6
Exp. Calc. Exp.[2] Calc. [our work] *
31800 32652 -852 30698 30883 -185
36400 35396 1004 40058 39998 60
38200 38333 -133 41929 41371 558
– 47327 – 43788 44259 -591
61000 61019 -19 48996 48959 37
* = Eexp [2] – Ecalc /our work/
European Social Fund
(Grants #MTT50,
MJD167, MJD054) and
RFBR #11-02-0248
support our work
Fig 1. The fluorescence decay kinetics from the 5d1(21) level of Ce3+:
(a) in the YPO4*0.8H2O: 0.2% Ce3+ NCs at laser excitation
(exc=266 nm, f=5 kHz, tp=9 ns, det=380 nm, T=300K); (b) in the YPO4: 2% Ce3+ bulk crystal (curve 1) and NCs (curve 2) at
synchrotron excitation
(exc=323 nm, f=5.21 MHz, tp=1 ns, det=355 nm, T=10K); the dash lines are fitting curves.
[1] B.Z. Malkin. Spectroscopy of Solids Containing Rare Earth Ions, 1987 (Elsevier) p. 13.
[2] L. van Pieterson, M.F. Reid, R.T. Wegh, et al, Phys. Rev. B, 65 (2002) 045113
149
PI_41 Optical spectroscopic study of the crystallization of B2O3:La2O3 glasses
doped with Nd3+
or Eu3+
D.S. Pytalev1)
, D. Caurant2)
1)
Institute of Spectroscopy, Russian Academy of Sciences, 142190, 5 Fizicheskaya St.,
Moscow, Troitsk, Russian Federation 2)
Laboratoire de Chimie de la Matière Condensée de Paris (UMR CNRS 7574) Ecole
Nationale Supérieure de Chimie de Paris (Chimie-ParisTech), 75005, 11 rue Pierre et Marie
Curie, Paris, France
B2O3:La2O3 binary glasses have been reported to possess excellent chemical durability and
high refractive index. They may be interesting host materials for optically active rare earth
(RE) ions substituting La. On the other hand, these glasses represent a simplified system to
study the structure and crystallization mechanisms which is important for searching and
optimizing new nuclear borosilicate glass compositions. Indeed, RE are one of the most
abundant families in radioactive wastes.
For this purpose, two glasses of composition 3B2O3.(La2O3)0.96.(RE2O3)0.04 with RE=Nd or Eu
were synthesized at 1250° C (30 min). Nd was chosen to perform optical absorption studies
while Eu was selected for luminescence studies. Two sets of heat treatments were performed
on glass powders (particle size range 40-125 μm) and bulk samples under air in a tubular
furnace at a constant temperature T = 771 ° C for various times (1-60 min) or for a fixed
period (5 min) but at increasing temperatures (771-801 °C). In all cases, the samples were
quenched to room temperature after treatment. The choice of heat treatment temperatures was
made based on the results of the differential thermal analysis (DTA).
Fig. 1. Transmission spectra of Nd-doped metaborate glasses treated during 5 min at different
temperatures.
Optical spectra of glasses with Nd3+
were measured at 8 K in the region of the 4I9/2→
4F3/2
transition (Fig. 1). For the non-treated sample, only two broad bands are observed
corresponding to the expected doublet of the Nd3+
ions located in a disordered environment.
With increasing the treatment time/temperature, narrow peaks, overlapping with the two
broad bands and corresponding to crystalline environment of Nd3+
, are observed. The spectra
point to the presence of several crystalline phases in the treated samples. They are, probably,
La3BO6, LaBO3, or LaB3O6 (a XRD study is in progress). Luminescence spectroscopy of
glasses doped with Eu3+
revealed a similar evolution of the RE ion environment under the
heat treatment.
150
PI_42 High-resolution optical spectroscopy of YPO4 doped with Tm3+
or Er3+
D.S. Pytalev1)
, M.N. Popova1)
, B.Z. Malkin2)
, M. Bettinelli3)
1) Institute of Spectroscopy, Russian Academy of Sciences, 142190, 5 Fizicheskaya
St.,Moscow, Troitsk, Russian Federation 2)
Kazan (Volga Region) Federal University, 420008, 18 Kremlyovskaya St., Kazan, Russian
Federation 3)
Dipartimento di Biotecnologie, University of Verona and INSTM, 37134, Verona, Italy
Tetragonal yttrium orthophosphate (YPO4) is a simple and well-known material. When doped
with rare earth (RE) ions, it demonstrates interesting optical, magnetic, and electronic
properties and finds useful applications in various quantum optical devices. Spectral
properties of YPO4:RE3+
were broadly studied, however, at low spectral resolution. Recently,
high-resolution optical spectroscopy has revealed the well-resolved hyperfine structure of
crystal-field levels of Ho3+
doped into YPO4 [1] which is of interest for possible quantum
memory applications.
In this work, we report on a high-resolution spectroscopic study of weakly doped YPO4:Tm3+
and YPO4:Er3+
crystals grown by flux method. For both compounds, the main spectral lines of
RE ions are accompanied by weak satellites. These satellites come, most probably, from the
RE ions that reside near impurities that may enter the crystal lattice from the flux during the
growth process [2]. Besides, a splitting of spectral lines due to electron-deformation and
hyperfine interactions was observed for the non-Kramers Tm3+
ion. The spectral line shapes
were computed using the distribution function of random strains produced by point defects in
the elastic continuum. A good agreement with the measured line shapes in the crystal
YPO4:0.2 at.% Tm3+
was achieved using the width of the strain distribution function =410-5
which was close to values of obtained earlier for hexafluoroelpasolites [3]. It should be
noted that in the present work a generalized approach was used, namely, in comparison with
the previous study, we took into account the totally symmetric strains that induce variations of
the gap between the crystal-field levels participating in the optical transition and lead to an
additional broadening of the observed spectral lines of Tm3+
.
This work was supported in part by the Russian Foundation for Basic Research (Grant No.
13-02-01091) and by the Russian Academy of Sciences under the Program “Fundamental
Optical Spectroscopy and its Applications”.
[1] M. Mazzera, R. Capelletti, A. Baraldi, E. Buffagni, N. Magnani, M. Bettinelli, J. Phys.:
Condens. Matter 24 (2012) 205501.
[2] M.N. Popova, K.N. Boldyrev, P.O. Petit, B. Viana, L.N. Bezmaternykh, J. Phys.:
Condens. Matter 20 (2008) 455210.
[3] B.Z. Malkin, D.S. Pytalev, M.N. Popova, E.I. Baibekov, M.L. Falin, K.I. Gerasimov, N.M.
Khaidukov., Phys. Rev. B 86 (2012) 134110.
151
PI_43 Ceramic planar waveguide structures for amplifiers and lasers
V.A. Konyushkin, A.N. Nakladov, D.V. Konyushkin, M.E. Doroshenko, V.V. Osiko,
A.Ya. Karasik
Prokhorov General Physics Institute Russian Academy of Sciences, 119991, Vavilov Str., 38,
Moscow, Russia.
E-mail: [email protected]
Ceramic and crystalline weakly guiding optical fibres with the core – cladding refractive
index difference of 10–2
– 10–4
are fabricated by a hot pressing method. The waveguides with
one or several cores for operation in the spectral range 0.2 – 5 mm are produced based on
CaF2, SrF2, and BaF2 ceramics and crystals and their solid solutions doped with trivalent Pr,
Nd, Tb, Dy, Yb, Ho, Er, and Tm ions, as well as based on LiF ceramics and crystals with
colour centres. The first results of investigation of the lasing properties of ceramic SrF2 : NdF
waveguides under diode pumping are presented, and the prospects of further investigation are
discussed.
We report here on the development of methods for fabricating planar (Fig. 1) ceramics
and crystalline weakly guiding waveguides with the core – cladding refractive index
difference Dn = n1 – n2 = 10-2
– 10-4
. For operation in the spectral range 0.2 – 5
mm, we designed PWs with one or several cores based on CaF2, SrF2, BaF2 fluoride
ceramics and crystals and their solid solutions. Ceramics and crystals for PWs were
doped with trivalent Pr, Nd, Tb, Dy, Yb, Ho, Er, and Tm ions. In addition, we
developed PWs based on LiF crystals with color centers.
For laser experiments, we chose a PW 15 mm long with a ceramic SrF2 : NdF3
core (NdF3 concentration 0.5 mol %, thickness 0.2 mm, width 7 mm) and a
crystalline SrF2 cladding. The waveguide laser slope efficiency of 4 % measured with
a 95 % output mirror is considerably lower than 37 % obtained for the crystal in. To
achieve a higher efficiency, it is necessary, in particular, to match the numerical
apertures of the pump beam and PW. This can be done without lens systems, using
instead of amultimode fibre and a lens only a waveguide with a small NA.
Fig 1. Microscope image of the facets of a Fig.2 Dependence of the output power of a
waveguide structure obtained by hot pressing laser based on an active planar waveguide
of a crystalline SrF2 cladding and a ceramic with a ceramic SrF2: NdF3 (0.5 mol %) core
SrF2 : NdF3 core. and a crystalline SrF2 cladding on the diode
pump power.
152
PI_44 Site-selective luminescence spectroscopy of rare earth ion doped
TiO2 nanoparticles
Ž. Antić, M.G. Nikolić, M. Marinović-Cincović, M.D. Dramićanin
Institute of Nuclear Sciences Vinča, University of Belgrade, P.O.Box 522, 11001 Belgrade,
Serbia
We investigated luminescence from Eu3+
and Sm3+
doped anatase TiO2 nanoparticles.
Material is prepared via hydrolytic sol-gel method and pure anatase phase was confirmed with
X-ray diffraction and transmission electron microscopy measurements. Site-selective
luminescence measurements performed at 10 K discover rare earth ion emissions from three
different crystallographic sites, Figure 1. We show that incorporation of larger ions into TiO2
and charge imbalance reduces site symmetry from D2d to C1 for site I, to C2v for site II and D2
for site III. Emission spectra from the lowest symmetry site I are quite broadened and can be
related to distorted sites near nanoparticle’s surface or other defects. Spectra from other two
sites (site II and site III) are composed of sharp emission lines, suggesting a crystalline
environment for rare earth ions (of strong covalency) and their incorporation into nanoparticle
volume.
In undoped anatase both sites have similar environment, being inside the scalenohedrons, with
local symmetry 42m (D2d). Titanium ions occupy sites in the smaller scalenohedron (site III,
volume 9.45 Å3) and vacancies are in the larger scalenohedron (site II, volume 13.26 Å
3).
After incorporation of larger RE3+
ions these sites reduce symmetries (remaining in the same
symmetry group) due to distortions. The environment of smaller site III takes disphenoidal
geometry (D2 local symmetry), while the larger site II takes pyramidal geometry (C2v local
symmetry).
Figure 1. a) Emission spectra of TiO2:Eu3+
from three sites: I - excited at 464.5 nm (C1), II -
excited at 467.6 nm (C2v) and III - excited at 468.3 nm (D2), and b) corresponding emission
decay curves.
153
Fig 1. The fluorescence emission rate of
CdSe/ZnS QDs, measured as a function of
their proximity to a dielectric lens. The
dashed line shows a theoretical fit to the
data (dots) using R=90 nm.
PI_45 Refractive index at the nanoscale
A . Aubret, J. Houel, A. Pillonnet, G. Ledoux, D. Amans, C. Dujardin, F. Kulzer
Institut Lumière Matière, UMR5306, Université Lyon 1-CNRS, Université de Lyon, 69622
Villeurbanne cedex, France
The refractive index, an inherently macroscopic quantity, can be difficult to define for
nanomaterials. This issue is particularly important for understanding the optical properties of
complex nanostructures formed by materials with different refractive indexes. Here, we show
how the sensitivity of individual nanoemitters to their immediate environment can be used to
measure the critical distance over which a local refractive index can be calculated [1,2].
We chose CdSe/ZnS core-shell quantum dots (QDs) as nanoprobes because it is well
established that the exciton relaxation dynamics of these particles depend strongly on their
local environment. Consequently, the luminescence rate of a given QD gives access to the
refractive index experienced by this emitter. The luminescence quantum yield of these
particular core/shell structures is known to be high, which serves to evaluate the suitability of
different theoretical models for the index-lifetime relationship. Moreover, the narrow
emission lines of QDs of different sizes allow us to study the critical distance over a large
spectral range. Our approach relies on the modification of the local dielectric environment of
a QD monolayer by the presence of a well-defined geometric object, a dielectric lens [2]. The
variations in the decay time of the monolayer as a function of the distance between the
emitters and the surface of this lens was observed with confocal microscopy.
The critical distance for the influence of the local environment was found to be around
90 nm (see Fig.1), based on the Bruggeman effective medium approach and a hard sphere
model. Furthermore, we did not observe any pronounced dependence of this distance on the
emission wavelength. To corroborate these results, a comparison with measurements of the
same emitters in different solutions and when deposited on substrates of various refractive
indexes, was carried out; all these experiments were found to be in good agreement. Our
results provide new perspectives for the use of quantum dots as nanoprobes for the
identification of materials through their refractive index.
[1] V. Lebihan and al., Physical Review B 78, 113405 (2008)
[2] A. Pillonnet and al., Optic Express 20, 158623 (2012)
154
PI_46 Interconfigurational 5d-4f luminescence of Pr3+
in phosphate hosts
Mattia Trevisani1)
, Konstantin Ivanovskikh2)
, Fabio Piccinelli1)
, Marco Bettinelli1)
1)
Laboratory of Solid State Chemistry, Department of Biotechnology, University of Verona,
and INSTM, UdR Verona, Strada Le Grazie 15, 37134 Verona, Italy 2)
Department of Physics and Astronomy, University of Canterbury, Private Bag 4800,
Christchurch 8020, New Zealand
Luminescent materials doped with Pr3+
are being actively investigated, as they can show
electric dipole allowed 5d-4f optical transitions located in the UV and visible regions. These
optical features find numerous applications in important technological fields, such as the
development of fast scintillators for detection of ionizing radiation (X-rays and γ-rays) [1].
The search for new materials showing efficient 5d-4f luminescence of the Pr3+
ion has led us
to the synthesis of several complex phosphates doped with this ion [2, 3].
The successful development of new scintillator materials requires the construction of an
adequate model for the energy transfer from the host to the emitting Pr3+
centres. In this
contribution recent results on the spectroscopy and relaxation dynamics of electronic
excitations in K3Lu(PO4)2 and KLuP2O7 doped with Pr3+
will be presented. Time-resolved
luminescence (emission and excitation) spectra and decay curves measured using UV-VUV
synchrotron radiation will be presented and discussed, together with the prospective
applications of these luminescent materials.
[1] C. Ronda, J. Gondek, E. Goirand, T. Jüstel, M. Bettinelli, A. Meijerink, Materials
Research Society Symposium Proceedings, 2009, 1111, 175.
[2] K. Ivanovskikh, A. Meijerink, C. Ronda, F. Piccinelli, A. Speghini, M. Bettinelli, Opt.
Mater., 2011, 34, 419.
[3] M. Trevisani, K. V. Ivanovskikh, F. Piccinelli, A. Speghini, M. Bettinelli, J. Phys.:
Condens. Matter, 2012, 24, 385502 (see also 489501).
155
PI_47 Laser spectroscopy of the Mn4+
– Mn4+
ion pairs in SrTiO3 crystal
L. R.Gilyazov1)
, S. I.Nikitin1)
, R. V.Yusupov1)
, A. Dejneka2)
, V. A.Trepakov2,3)
1)
Kazan Federal University, Kremlevskaya 18, Kazan, Russia 2)
Institute of Physics AV CR, Na Slovance 2, 18221, Prague 8, Czech Republic 3)
Ioffe Physical-Technical Institute RAS, 194021 St-Petersburg, Russia
During the last few decades the perovskite-structure oxides were extensively studied
due to the observation of various unusual phenomena like high-temperature
superconductivity, colossal magnetoresistance and metal-to-insulator transitions. Strontium
titanate SrTiO3 (STO) is a famous representative of this family. Manganese-doped STO
(STO:Mn) has attracted much attention recently revealing both the ferroelectric and
ferromagnetic properties at low temperatures. The origin of these intriguing phenomena is not
quite clear still, but undoubtedly related to the Mn impurity. The electron paramagnetic
resonance (EPR) studies have shown that different centers are formed in STO:Mn crystals:
single Mn4+
, Mn3+
and Mn2+
ions and Mn-ion centers associated with the oxygen vacancies.
Also, the Mn4+
– Mn4+
ion pair observation in the EPR spectra was reported with the Mn-ions
located in the next-nearest Ti-sites along the [110] crystal axis [1]. At the same time nothing
was known about the optical properties of these pairs as well as the energy level structures in
the ground and excited states. This is not surprising as the amount of these centers is small,
the spectra overlap with the lines of the single Mn4+
ions. High-resolution laser spectroscopy
is a powerful method allowing to overcome the mentioned difficulties.
We report on the first observation of the luminescence and excitation spectra of the
Mn4+
– Mn4+
ion pairs in high quality Verneuil grown STO:Mn single crystal (Figure) from
Furuuchi Chemical Corporation.
The 4 4
2 2,g gA A ground state energy level scheme has been unambiguously established. It is
well described by the antiferromagnetic isotropic exchange interaction with J = 8.16 cm-1
.
The structure of the excited 4 2
2 ,g gA E
state is more complicated due to the
orbital and permutation degeneracies.
Assignment of the observed lines will be
discussed.
Observation of a d-ion pair in the
optical spectra of the doped crystals is
often explained by the exchange inducing
of the transitions that are spin-forbidden
for a single ion. However, the case of the
Mn4+
– Mn4+
pair in STO crystal doesn’t
follow this trend. The most intense lines
in the spectra correspond to the transitions
with 1S selection rule, not 0S ,
where S is a total spin of the pair. Probably, the same peculiarities of the pair have not
allowed us to define its symmetry by means of the polarized luminescence studies that were
proposed by P.P. Feofilov [2]: the anisotropy was much smaller than it was expected.
1. D. V. Azamat, A. Dejneka, J. Lancok, V. A. Trepakov, L. Jastrabik, and A. G. Badalyan, J. Appl.
Phys. 111, 104119 (2012).
2. P. P. Feofilov. The physical basis of polarized emission. Consultants Bureau, NY, 1961.
720 722 724 726 7280.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty,
10
4 c
ounts
/s
, nm
T=8 K Mn4+
excitation
luminescence
156
PI_48 Selective Laser Spectroscopy of BaF2:Yb3+
Crystals
S. L. Korableva, I. E. Mumdzhi, S. I. Nikitin
Kazan Federal University, 420008, Kremlevskaya 18 St, Kazan, Russia
e-mail: [email protected]
Fluoride crystals doped with RE ions are the traditional objects for investigations by
EPR and optical spectroscopy methods. These crystals are very attractive materials as active
media for powerful lasers and fast scintillators due to their excellent thermo-physical
characteristics and possibility large bulk crystals production. EPR spectroscopy of Yb3+
ions
in Ba1-xLaxF2+x mixed crystals indicates the formation of linear type La-F-Yb-F or Yb-F-Yb-F
(x=0) clusters with trigonal symmetry, and no trace of the tetragonal symmetry centers have
been found [1,2]. Optical spectroscopy has also evidenced the formation of some kind of Yb3+
clusters, which start dominate with Yb3+
concentration above 0.1%. Furthermore, the
suggestion was made that the active laser centers in BaF2 crystal are the hexameric clusters of
Yb3+
ions [3]. Spectroscopic properties of such clusters have not been fully studied [4]. The
scope of this investigation is to determine the structure and the symmetry of Yb3+
-clusters in
BaF2 by site-selective laser spectroscopy methods in high magnetic field.
BaF2:Yb3+
crystals were grown by Bridgman–Stockbarger method in graphite
crucibles. Analysis of luminescence spectra, luminescence excitation spectra and cooperative
luminescence properties indicates the formation of several types of Yb3+
ion clusters in
BaF2:Yb3+
crystal. We suppose that a great variety of such clusters is due to distortions of the
parent cluster. To establish the symmetry of these undistorted parent cluster, the magneto-
optical method have been used. The angular dependence of ground state splitting in magnetic
field reveals tetragonal character unlike of the linear type Yb-F-Yb-F clusters discussed in [2].
The estimated g-factor values in the ground state are g||=4.16 and g=2.27. Stark structure of
the energy levels of Yb3+
ions in these undistorted clusters is close to the level structure of
Yb3+
ions in KY3F10 crystal [5]. The nearest environment of Yb3+
ions in KY3F10 crystal form
an antiprism which has a structure similar to the hexameric clusters of rare-earth ions [4]. All
these facts allows to suggest that observed clusters of Yb3+
ions in BaF2 crystal are hexameric
clusters.
[1] L. K. Aminov, R. Yu. Abdulsabirov, M. R. Gafurov et al. Appl. Magn. Reson. – 2005. –
Vol. 28, P. 41-53
[2] L. K. Aminov, I. N. Kurkin, Physics of the Solid State - 2009, - Vol. 51, No. 4, P. 741–
743.
[3] P. Camy, J. L. Doualan, A. Benayad et al. Appl. Phys. B. - 2007. - Vol. 89. - P. 539
[4] S. A. Kazanskii, A. I. Ryskin, A. E. Nikiforov et al. Phys. Rev. B. – 2005. – Vol. 72,
014127.
[5] M. Ito, G. Boulon, A. Bensalah et al. J. Opt. Soc. Am. B. – 2007. – Vol. 24, No. 12. – P.
3023
157
PI_49 Optical properties and photoinduced magnetism in -Fe2O3 semiconductor
nanoparticles formed in liquid crystalline poly(propylene imine) dendrimer
N.E. Domracheva1)
, V.E. Vorobeva1)
, A.V. Pyataev2)
, M.S. Gruzdev3)
1)
Zavoisky Kazan Physical-Technical Institute, Russian Academy of Science, 420029,
Sibirsky Tract 10/7, Kazan, Russia 2)
Kazan Federal University, 420008, Kremlyovskaya St. 18, Kazan, Russia 3)
G.A. Krestov Institute of Solution Chemistry, Russian Academy of Science, 153045,
Akademicheskaya St. 1, Ivanovo, Russia
Gamma-iron oxide is technologically useful material since the stability and semiconductor
properties allow it to be used in photoelectrochemistry such as solar energy conversion, water
splitting, photocatalysts, while the magnetic properties make it a common active component
of high-density recording media.
Here, we present the first results of investigation of the optical properties and the influence of
light on the magnetic properties of ultrafine ferrimagnetic -Fe2O3 nanoparticles (NPs) created
in the liquid crystalline second-generation dendrimer. It has been shown earlier [1] that the
mean diameter of NPs formed in the dendrimer is 2.5 nm and the particles are
superparamagnetic with a blocking temperature about 60 K (below which the anisotropic
interactions dominate and the superparamagnetism is lost).
The electronic absorption spectra of -Fe2O3 NPs demonstrate a particle size effect. The
semiconductor exhibits the absorption with two bands at ~ 230 and ~ 257 nm and a tail
extending to ~ 560 nm. The optical absorption studies show a band gap of 4.61 eV, which is
blue shifted by 2.41 eV when compared to the reported value of the bulk material (2.2 eV).
This shift is explained on the basis of quantum confinement, due to the molecular character of
the wave function of the NPs.
Samples with the randomly and partially oriented NPs obtained, respectively, under zero-
field-cooling (ZFC) and field-cooling (FC) regime display a different behavior upon
irradiation. Irradiation of the ZFC sample held in vacuo at 6.9 K with the wavelength 266 nm
caused the appearance of new EPR signal at g = 2.0 with a line width 730 G (fig. 1).
The signal decays immediately when the irradiation is stopped. The growth and decay of the
signal upon irradiation can be reproduced many
times at 6.9 K. We suggest that the generation
of conduction band electrons by irradiation into
the band gap of the -Fe2O3 moderates the
magnetic coupling between iron ions in NPs.
Irradiation of the FC sample does not show
such effect. This effect is largely suppressed in
the presence of adsorbed oxygen, which can
scavenge the conduction band electrons.
Fig. 1. EPR spectrum recorded at 6.9 K during irradiation
of -Fe2O3 in vacuo with 266 nm light (solid line). The
dashed trace shows the spectrum of the same sample in
the dark.
[1] N.E. Domracheva, A.V. Pyataev, R.A. Manapov, M.S. Gruzdev. ChemPhysChem (2011)
12, 3009-3019
158
PI_50 Yb2+
content in laser CaF2:Yb3+
crystals and ceramics
A.S. Shcheulin
1, A.E. Angervaks
1, P.P. Fedorov
2, V.M. Reiterov
3, E.A. Garibin
3 and
A.I. Ryskin1
1National Research University of Information Technologies, Mechanics and Optics, 197101,
Kronverkskiy pr. 49, St. Petersburg, Russian Federation 2General Physics Institute Moscow Russian Federation
3INCROME Ltd., ul. Babushkina 36, 192171, St. Petersburg, Russian Federation
The trivalent ytterbium ion, when compared with the widely used neodymium ion, has
significant advantages as a dopant of diode-pumped lasers media. Since the first laser studies
of CaF2:Yb crystals, this medium has attracted a growing interest for use in short-pulse, high
power, high-energy solid-state lasers When growing CaF2 crystal doped with rare earth ions,
most of these ions are present in a trivalent state. However, due to contact with graphite
crucible, a small proportion of a number of ions (Eu, Sm, Yb and Tm) are reduced to a
bivalent state. A similar situation takes place during fabrication of CaF2 ceramics doped with
rare-earth metals. This fact is of particular importance for laser CaF2:Yb crystals (ceramics), a
promising material for short-pulse, high-power, high-energy diode-pumped solid state lasers
since the presence of bivalent Yb ions can be a source of thermal losses. To date, there has
been no technique to determine Yb2 concentration in as-grown crystals. The proposed
technique is based on a total reduction of Yb3 ions via the heating of as-grown CaF2 crystals
with known concentration of Yb in the reducing atmosphere of metal vapour and determining
the cross section of absorption bands of Yb2 ions. The knowledge of these parameters allows
estimation of the Yb2 content in CaF2:Yb crystals or ceramics by analysing their absorption
spectra. Examples of using this technique are given. An additive colouring technique has been
used for the total conversion of Yb3 ions in low-concentration CaF2:Yb crystals into a bivalent
state. Significant distinctions in the colouring of undoped and RE-doped crystals have been
found. The colouring of RE-doped crystals is occurring much slower than compared to
undoped crystals, the border between coloured and non-coloured segments of the samples is
considerably more distinctive, and the concentration of anion vacancies/electrons introduced
into the samples at its colouring is much higher. The physical mechanisms responsible for
these distinctions are discussed. It was found that for crystals with Yb concentration that do
not exceed ~6 x 1018
cm-3
, the colouring conditions used in this study ensure the total
conversion of Yb3 ions presentin the crystal into a bivalent state. This fact made it possible to
find the cross-sections of several Yb2 absorption bands. The knowledge of these parameters
allowed estimation of the Yb2 content in as-grown CaF2:Yb crystal and two samples of
CaF2:Yb ceramics, as-fabricated and fluorinated after the fabrication. The technology of CdF2
crystals reduction (an ‘‘additive colouring’’) and features of colouring of crystals doped with
rare-earth ions are considered.
159
Poster session II
160
PII_1 Molecular structure and magnetic properties of Mn2+
-Ag2+
pairs formed
in BaF2 crystals: EPR data
E.R. Zhiteitsev1)
, V.A. Ulanov1,2)
, R.R. Zainullin2)
, A.M. Sinitsyn2)
1)Zavoiskii Kazan Physical Technical Institute, 420029, Pionerskaja str., 7/10, Kazan, Russia
2)Kazan State Power Engineering University, 420066, Krasnoselskaja str., 51, Kazan, Russia
The alkaline-earth fluorides (MeF2) are important models for understanding the solid-state
chemistry of point defects in insulating crystals. The extensive experimental and theoretical
investigation of these systems has resulted in a detailed microscopic picture on physical-
chemical reactions between native and impurity defects. Most of these works were devoted to
the fluorite type crystals (CaF2, SrF2 and BaF2) doped with trivalent rare-earth ions. It was
motivated by their ability to accommodate large molar fractions of trivalent rare-earth
impurities. Relatively a few works were devoted to reactions between impurity d-ions in
fluorite type crystals.
Our investigations of the solid-state reactions between defects of impurity d-ions reveal a
possibility to synthesize paramagnetic impurity clusters of two [1, 2] or three [3] similar d-
ions. It was found that each of these ions substitutes for a lattice cation and find itself in the
center of an anionic cube formed by eight fluorine ions. If the ion is Jahn-Teller type its
anionic neighbors relax to new equilibrium positions. A field of Jahn-Teller deformations
appears around the Jahn-Teller ions. The ground state of Jahn-Teller ion becomes an orbital
singlet. When the distances between impurity ions become short enough they can form a
cluster due to interaction via the fields of Jahn-Teller deformations. Another mechanism of
cluster formation is an electronic exchange between the impurity ions.
The present work was devoted to impurity pairs of non-similar d-ions. The first object of the
present investigation was BaF2 crystal doped by manganese and silver impurities. The
samples under investigation were grown by Bridgman method. The EPR method was used to
study the magnetic properties, molecular structure and relative concentration of Mn-Ag pairs
(X-band, T = 4.2K). The anisotropic spectra with fine, hyperfine and superhyperfine
structures were revealed in the samples.
It was found that the magnetic
symmetry of the Mn-Ag pairs was
tetragonal (fourfold axis C4 was parallel
to a crystallographic <001> axis). Spin
momentum of Mn-Ag pair centre was
S = 2. The latest fact speaks about
antiferromagnetic exchange between
Mn2+
and Ag2+
ions forming the pair
centre. One fine structure component of
the EPR spectrum recorded in
perpendicular orientation (C4
H0||<010>) is shown in Fig1. As it can
be seen the spectrum contains very
reach information on the molecular structure and magnetic properties of the pairs under
investigation. The results of calculations will be presented in the article.
The work is supported by Russian Foundation of Basic Research, grant 12-02-31148.
[1] E.R. Zhiteitsev, M.M. Zaripov, V.A.Ulanov. Fizika Tverdogo Tela, 47, 1212 (2005)
[2] I.I. Fazlizhanov, V.A. Ulanov, M.M. Zaripov. Fizika Tverdogo Tela, 44,1483 (2002).
[3] V.A. Ulanov, M.M. Zaripov, I.I. Fazlizhanov. Fizika Tverdogo Tela, 47,1596 (2005).
161
PII_2 EPR observation of lattice instabilities in narrow gap semiconductor PbTe
doped by Mn2+
impurity ions
V.A. Ulanov1,2)
, A.M. Sinitsyn1)
, R.R. Zainullin1)
, E.R. Zhiteitsev2)
1)Kazan State Power Engineering University, 420066, Krasnoselskaja str., 51, Kazan, Russia
2)Zavoiskii Kazan Physical Technical Institute, 420029, Pionerskaja str., 7/10, Kazan, Russia
The semiconducting lead chalcogenides PbS, PbSe and PbTe with the cubic rock salt structure
have been the subject of a vast amount of theoretical and experimental work. It was motivated
not only by their technological applications, but also by their unusual physical properties.
Lead chalcogenides are narrow gap semiconductors with strong ionic character. They have a
positive temperature coefficient of the gap (dE/dT > 0), the high static dielectric constant, and
the large carrier mobility. These properties make them unique among polar compounds and
have important applications in many fields, such as infrared detectors, light-emitting devices,
infrared lasers, thermoelectric materials and solar energy panels. Studies about
heterostructures, films, quantum wires and quantum dots or wells of lead chalcogenides and
their applications have caused much attention in the past decades. But, a little of these studies
were performed by EPR method. The reason of the latest fact is that most of the paramagnetic
impurity centers form resonant levels in the conduction or valence band in the lead
chalcogenides and all such centers are not observable by EPR method.
Fortunately it was found [1] that the d-electrons of Mn2+
ions embedded in the lead
chalcogenides are well localized at the Pb sites and form local magnetic moments. Owing to
the direct exchange interaction between the d-electrons and the valence-band Bloch electrons,
the latter are magnetically polarized. Through these polarized electrons, the local spins of
Mn2+
ions interact with each other and with another paramagnetic impurity ions being in
resonant states. Consequently, the manganese impurity centers can be used as paramagnetic
probes to study some physical properties of the lead chalcogenide semiconductors codoped by
two or more kinds of paramagnetic impurities. But, one problem arises there. It is associated
with the fact that in the lead chalcogenides an increasing of impurity ion concentration is
associated with increasing of number of native defects. At high concentrations of native
defects and free carriers the Mn2+
spectrum becomes very complicated.
We report here the EPR data on deep Mn2+
centers in Pb1-xMnxTe (0,001 < x < 0,02). X-band
EPR measurements were performed on single crystals Pb1-xMnxTe grown by Bridgman
method in quartz crucibles. The samples were mounted in a two-circle goniometer and rotated
in the (110) crystallographic plane. The measurements were carried out at liquid helium
temperature (4.2 K). Six principal Mn2+
hyperfine lines were observed in the EPR spectra.
The field intervals between the lines were found to be isotropic under rotation in the (110)
plane within the experimental error of about 0.1 G. Each of these hyperfine lines was found
to be surrounded by satellites in the orientations H0||<111>. Field positions of the satellites
were dependent on magnetic field direction. The structure formed by each hyperfine line and
its satellites was like the fine-structure of the EPR spectra of the cubic Mn2+
centers distorted
trigonally. But, intensities of the satellite lines were significantly lower than it can be found
for manganese centers in a wide gap semiconductor (5:8:9:8:5). Above mentioned satellite
lines were not registered in the Pb1-xMnxTe samples with x ~ 0.001. In latest the EPR lines
were narrowed and superhiperfine structure from the nuclear magnetic moments of isotopes 125
Te was observed. The results are interpreted in terms of local lattice instability induced by
Mn2+
ions.
[1] Ven-Chung Lee. Phys. Rev. B, 34, 5430 (1986).
[2] J.H. Pifer. Phys. Rev., 157, 272 (1967).
162
PII_3 Fe3+
-Cl-, Fe
3+-Br
-, Fe
3+-О
2-, Fe
3+-OH
- dimer centers in the ferroelectric lead
germanate
V. A. Vazhenin, A. P. Potapov, A. V. Fokin, and M. Yu. Artyomov
Institute of Physics and Applied Mathematics, Ural Federal University, 620000, pr. Lenina
51, Yekaterinburg, Russia
E-mail: [email protected]
In [1], the ferroelectric lead germanate single crystals doped with iron and annealed in a
chlorine-containing atmosphere was studied using electron paramagnetic resonance method
and the signals of three triclinic Fe3+
complexes were detected in the vicinity of the transitions
of trigonal Fe3+
centers [2] with large zero-field splitting (b20 25GHz). The investigation of
the samples annealed in bromine- or fluorine-containing atmosphere performed by us showed
the formation of new triclinic complexes (see Fig.).
The analysis of the orientational behavior of the
positions of transitions allowed us to determine the
second rank parameters of spin Hamiltonian with
good description of experimental data for all
observable paramagnetic centers. It is clear that the
values of the diagonal parameters of the triclinic
complexes are slightly different from the trigonal
ones.
Fig. EPR spectrum in the vicinity of transition 1/23/2 of
the trigonal Fe3+ center for BC3 and at room temperature.
a – initial sample, b – after annealing with ZnCl2, с - after
annealing with CsBr, d - after annealing with PTFE
(teflon).
Therefore we assume that triclinic complexes
correspond to Fe3+
ions in a trigonal lead positions
associated with anions allocated in the interstitial
channels of the structure (Fe3+
-Cl-, Fe
3+-Br
-, Fe
3+-О
2- or Fe
3+-ОH
-). It is these anions are
located in channels in related compounds (apatite and nasonite). Similar dimer complexes
(Gd3+
-Cl-, Gd
3+-Br
-, Gd
3+-О
2-) were studied in lead germanate crystals with gadolinium [3].
The formation of Fe3+
-О2-
or Fe3+
-ОH- dimer complexes in samples at annealing in presence
of PTFE may be connected with substitution of oxygen positions by F- ions [4]. On the basis
of the analysis of interrelations between parameters of observed complexes and their
temperature behavior, the localization of charge-compensating anions in interstitial channel is
discussed.
[1] V. A. Vazhenin, A. P. Potapov, A. V. Fokin, M. Yu. Artyomov. Physics of the Solid
State 54, 2450 (2012).
[2] V. A. Vazhenin, A. D. Gorlov, K. M. Zolotareva, A. P. Potapov, A. I. Rokeakh, and
Yu. A. Sherstkov, Sov. Phys. Solid State 21, 158 (1979).
[3] V. A. Vazhenin, K.M. Starichenko, A.V. Gur’ev, L.I. Levin, F.M. Musalimov. Fiz.
Tverd. Tela 29, 409 (1987).
[4] A.A. Bush, Yu.N. Venevtsev. Izv. Akad. Nauk. SSSR Neorg. Mater. 17, 302 (1981).
1350 1400 1450
d
c
b
B, mT
a
163
PII_4 Quasi-cubic (tetragonal) Gd3+
centers in Ca1 – xYxF2+ x
V. A. Vazhenin, A. P. Potapov, A. V. Fokin, and M. Yu. Artyomov
Institute of Physics and Applied Mathematics, Ural Federal University, 620000, pr. Lenina
51, Yekaterinburg, Russia E-mail: [email protected]
The EPR spectrum of Ca1–x–yYxGdyF2+x+y single crystals exhibit an intense Gd3+
cubic center
caused by individual gadolinium ions, whose parameters of the spin Hamiltonian within the
experimental error coincide with those of the cubic centers in yttrium-free crystals. In
addition, the spectrum exhibits the signals of tetragonal Gd3+
–F-i dimer centers (F
-i is an
interstitial fluorine ion), whose intensity relative to the signal of cubic centers is much lower
than in CaF2.
The new EPR spectrum of the yttrium-doped calcium fluoride samples has the maximum
width (400 mT) at B ||C4. The resonance positions of the majority of the spectral
components (first of all, of the peripheral ones) have extreme values at this orientation. These
features of the spectrum are typical for the centers of predominantly tetragonal symmetry, in
agreement with the earlier results [1-2]. By the analysis of the magnetic resonance spectra of
Er3+
, Tm3+
, and Yb3+
in yttrium and lutetium-doped CaF2 crystals, Kazanskii et al. [1-2] found
that paramagnetic rare-earth ions are localized in octahedral yttrium or lutetium clusters.
The investigation of the transformation of the spectrum near the transitions of the cubic Gd3+
center with a change in the orientation of the magnetic field in the C4–C2 and C4–C3 plane
revealed the presence of weak satellites of these signals, which exhibit the orientational
behavior near B || C4 similar to that of the cubic center. The spectrum of one set of satellites
(the possibility of the existence of other weaker and poorly resolved satellite centers cannot be
excluded) can be described by the spin Hamiltonian (S = 7/2) with the tetragonal symmetry.
The main difference between the tetragonal (quasi-cubic) and cubic centers is the presence of
the axial parameter b20 for the former ones. It can be assumed that the discovered centers are
caused by individual Gd3+
ions situating near the octahedral rare-earth clusters or their groups.
Owing to a difference in size between the rare-earth supercluster and the substituted fragment
of the fluorite structure, the nearest anionic neighborhood of such centers should quite
probably form a truncated square pyramid. The superposition model [3] with parameters [4]
was used for estimation of the b20, b40, b44 values of quasi-cubic centers. A fair agreement
between the experimental and calculated values can be regarded as a valuable argument in
favor of our assumption on the origin of quasi-cubic (tetragonal) centers.
It should be mentioned that many transitions of tetragonal Gd3+
–F-i dimer centers are also
accompanied by satellites with similar orientational behavior. Most probably, these satellite
signals are caused by the tetragonal Gd3+
–F-i dimer centers situated near the cluster
formations.
[1] S.A. Kazanskii, Sov. Phys. JETP 62 (4), 527 (1985).
[2] S.A. Kazanskii, A.I. Ryskin, A.E. Nikiforov,A.Yu. Zaharov, M.Yu. Ougrumov, and G.S.
Shakurov, Phys. Rev. B: Condens. Matter 72, 014127 (2005).
[3] D.J. Newman and W. Urban, J. Phys. C: Solid State Phys. 5, 3101 (1972).
[4] A. Edgar and D.J. Newman, J. Phys. C: Solid State Phys. 8, 4023 (1975).
164
PII_5 Anisotropy of the g-tensor and spin-spin interaction
in dimer dysprosium(III) complex
R. Galeev1)
, A. Sukhanov1)
, R. Eremina1)
, V. Voronkova1)
, A. Baniodeh2)
, A. K. Powell2)
1Zavoisky Physical-Technical Institute, Russian Academy of Sciences, 420029 Sibirsky
tr.10/7, Kazan, Russian Federation 2Karlsruhe Institute of Technology, University of Karlsruhe, D-76131 Engesserstr. 15,
Karlsruhe, Germany
The design of single-molecule magnets (SMMs) has become a hot area of research due to the
potential applications of such compounds in new storage and information-processing
technologies [1]. Clusters containing dysprosium ions have recently attracted much attention
as perspective candidates for the design of new SMMs. Indeed, the Dy(III) ions in the low-
symmetry environment have a strong magnetic anisotropy at low temperature and there are
examples of dysprosium complexes showing SMM behaviors [2,3]. The anisotropy of local
magnetic properties of Dy (III) ions plays a decisive role in the formation of this property.
In spite of the great success obtained with ab initio methods in the theoretical
description of the possible ground states and anisotropy of Dy(III) containing compounds, the
real data for the control of the magnetic anisotropy is not enough. We here present a study by EPR of the local magnetic anisotropy of Dy (III) ion and spin-spin
interaction in the model system built up of Dy-Dy dimers. The centrosymmetric dimer is composed of
two nine-coordinate Dy(III) ions bridged by two oxygen atoms and a Dy-Dy distance is 0.38
nm. The EPR measurements were made on a Bruker EMX/plus spectrometer equipped
ER4102ST X-band resonator and a 4116DM dual mode resonator and on Bruker Elexsys E-
580 in Q-band. We carried out measurements of the temperature dependence of EPR spectra
from 4K to 290K and the numerical calculations of the EPR spectra for X- and Q-bands.
Fitting of the simulated and experimental spectra in X- and Q-bands allows us to determine
the g-tensor of Dy (III) ions and tensor of the anisotropic spin-spin interaction. EPR study
showed the unusual for Dy(III) ion anisotropy of the g-tensor and large anisotropy of spin-
spin interaction. Theoretical calculations of the g-tensor for this dimer were made in the
model crystal field taking into account the structural data and a varying the electronic
densities on the ligands of the nearest environment.
This research is supported in part by the Russian Foundation for Basic Research (project no.
13-02-01157) and the President of the Russian Federation (grant no. NSh-5602.2012).
[1] Affronte M., Troiani F., Ghirri A.: J. Phys. D 40, 2999 (2007).
[2] Ishikawa N.: Struct. Bond. 135, 211 (2010).
[3] Long J., Habib F., Lin P.-H. et al. J. Am. Chem. Soc. 133, 5319 (2011).
165
PII_6 EPR of [Fe2Dy2(OH)2(teaH)2(R-C6H4COO)6] clusters, R = p-NC, m-NC
A. Sukhanov1)
, V. Voronkova1)
, A. Baniodeh2)
, A. K. Powell2)
1Zavoisky Physical-Technical Institute, Russian Academy of Sciences, 420029 Sibirsky
tr.10/7, Kazan, Russian Federation 2Karlsruhe Institute of Technology, University of Karlsruhe, D-76131 Engesserstr. 15,
Karlsruhe, Germany
Recently [FeIII
2LnIII
2(3-OH)2(teaH)2(O2CCPh)6]·3MeCN compound built up of tetranuclear
Fe2Ln2 cluster was investigated using a combination of experimental techniques and
theoretical studies [1]. AC magnetic measurements for the Fe2Dy2 cluster showed the slow
magnetic relaxation with the effective energy barrier Ueff=16.21K. This indicates the single-
molecule magnet behavior of the Fe2Dy2 cluster. The DyIII
ions in low-symmetry
environment have a strong magnetic anisotropy at low temperature and the magnetic
anisotropy and orientation of the easy axis of the magnetization of the DyIII
ion depend
strongly on the ligand environment. The study of a family of clusters with different para-
substituted benzoate ligands [Fe2Dy2(OH)2(teaH)2(R-C6H4COO)6] showed how minor
changes of the electronegativity in the ligand sphere and the donor-acceptor nature of the
ligands control the magnetic anisotropy of the dysprosium ion [2].
We present results of the EPR study of two heteroclusters [Fe2Dy2(OH)2(teaH)2(R-
C6H4COO)6], R = p-NC, m-NC. The EPR spectra of polycrystalline samples were measured
at X- and Q-bands in the temperature range of 290-4 K. The low-temperature spectra were
described in the model taking into account the strong anisotropic Zeeman and dipole-dipole
interactions between two DyIII
ions. The analysis indicated that the change the position of the
CN group from para- to meta-position affects the orientation of the easy axis of the
magnetization of the DyIII
ion.
This research is supported in part by the Russian Foundation for Basic Research (project no.
13-02-01157) and the President of the Russian Federation (grant no. NSh-5602.2012).
[1]. A. Baniodeh, Y. Lan, Gh. Novitchi, et al. Dalton Trans. – 2013. –
DOI:10.1039/C3DT00105A.
[2]. V. Mereacre, A. Baniodeh, C. E. Anson, A. K. Powell, J. Am. Chem. Soc. - 2011.-
V.133.- P.15335.
166
PII_7 EPR investigations of 3d-4f interactions in trinuclear cluster Dy2Fe
A. Sukhanov1)
, V. Voronkova1)
, A. Baniodeh2)
, A. K. Powell2)
1)
Zavoisky Physical-Technical Institute, Kazan, Russian Federation 2)
Karlsruhe Institute of Technology, University of Karlsruhe, Karlsruhe, Germany
In the past decade, molecular spin clusters based on 3d-4f ions have attracted much
attention due to the presence of slow magnetic relaxation in such clusters at low temperature
[1]. Such clusters named single molecule magnets (SMMs) [2]. The use of such SMMs would
be able to develop of nanoengineering and microelectronics. But major disadvantage of the
existing SMMs is a very low operating temperature (2–3 K). Knowledge of the nature
interactions in such SMMs is necessary for effective creation of new SMMs for real
applications.
Previously we studied tetranuclear clusters Fe2Ln2 (Ln= Ce3+
, Pr3+
, Nd3+
, Sm3+
, Eu3+
,
Gd3+
, Tb3+
, Dy3+
, Ho3+
, Er3+
, Tm 3+
, Yb3+
, Y3+
) [3]. It was shown that the cluster Fe2Dy2 has a
slow magnetic relaxation at low temperature. In this work the study of new isostructural
compounds C50H67.46Dy2Fe1.18N7O23 (Dy2Fe) and C50.4H68.64Fe1.12Y2N6.8O23.2 (Y2Fe) by EPR
spectroscopy is presented. Compounds Dy2Fe and Y2Fe had an impurity tetranuclear clusters
Dy2Fe2 (22%) and Y2Fe2 (14%), respectively. We carried out the measurements of the
temperature dependent EPR spectra at X- band. The analysis of the spectra was performed
using simulations of EPR spectra. The EPR spectra were simulated in the model taking into
account the single-ion anisotropy term DFe, dipole-dipole interactions.
The analysis of the EPR spectra for these clusters allows us to assume that only
dipole-dipole interactions are realized between dysprosium and iron ions. Simulation of the
EPR spectra was performed using Matlab toolbox 'EasySpin' [4].
This work was supported by the Grant of the President of RF (MK-6407.2012.2) and by the
Russian Foundation for Basic Research (project no. 13-02-01157).
[1] A [Mn18Dy] SMM resulting from the targeted replacement of the center MnII in the S
=83/2 [Mn19]-aggregate with DyIII. Ayuk M. [et al.] Chem.Commun. (2009), 544–546.
[2] Molecular Nanomagnets. Dante Gatteschi, Roberta Sessoli, Jacques Villain. Oxford
University Press (2006). 395 p. – ISBN 0-19-856753-7.
[3] Magnetic anisotropy and exchange coupling in a family of isostructural FeIII
2LnIII
2
complexes. A. Baniodeh [et al.], Dalton Trans. (2013). – DOI:10.1039/C3DT00105A.
[4] EasySpin, a comprehensive software package for spectral simulation and analysis in EPR/
S. Stoll [et al.] J. Magn. Reson. (2006) Vol.178, 42-55.
167
PII_8 ESR linewidth near the nematic-smectic transition
B.M. Khasanov
Kazan Federal University, 420008, 18 Kremlyovskaya St., Institute of Physics, Kazan, Russia
Magnetic resonance relaxation experiments have been very useful in the study of the
dynamical properties of liquid crystals. Pretransitional effects which are manifested as critical
anomalies in relaxation measurements, are caused by long-rang cooperative modes, associated
with the quasicritical fluctuations in the ordering at phase transitions.
Several electron spin resonance (ESR) relaxation studies at nematic-isotropic (N-I), and
nematic-smectic A (N-Sa) phase transitions were performed using different nitroxide spin
probes dissolved in .nO m homologous liquid crystal series [1,2,3]. The ESR spectra were
motionally narrowed. This permits a linewidth analysis as a function of the 14N nuclear spin
quantum number m , 2
21 T A Bm Cm . Critical type divergences were observed at N-I
and N-Sa transitions for all the hyperfine lines.
The fluctuations in the nematic order parameter can result in a slowly fluctuating
orientational potential at the site of the probe molecule, thus modulating the rotational
reorientation of the probe. Such modulations lead to anomalous effects in spin relaxation and
divergences for the hyperfine lines [1].Near the N-Sa phase transition ESR probes typically
undergo partial expulsion from the orientationally well ordered aromatic cores of the liquid
crystal molecules toward less ordered aliphatic regions. The formation of smectic clusters is
described by density fluctuations and the movement of the probe molecules affects the order
parameter and rotational correlation time of the probe. Thus density fluctuations modulate the
molecular dynamics and spin relaxation of the probe [2]..
However, the P-probe (2,2’,6,6’-tetramethyl 4-(butyloxy) benzylamino-piperidine N-oxide),
which is similar in structure to a liquid crystal molecule and exhibits the ordering and
dynamics similar to that expected for the host molecules do not expelled from core region.
The observation of significant divergences for the P-probe in 7 .5O liquid crystal with a very
narrow (~4C) nematic range, suggests that the direct coupling between orientational and
positional order parameters can play a significant role when the orientational order parameter
is not saturated. Here we predict a universal behavior of the non-order parameter orientational
field near the N-Sa phase transition. We show that the inverse nematic susceptibility develops
a finite drop near the N-Sa transition and lead to the rather strong divergence in B and C
parameters in the linewidth.. Thus our predictions seem to reproduce well the general features
of experimental data [3] when the former, expulsion model, do not play a role in influencing
relaxation near the N-Sa transition.
[1] A. Nayeem, S.B.Rananavare, V.S. Sastry, J.H. Freed, J. Chem. Phys. 96, 3912 (1992)
[2] S.A. Zager, J.H. Freed, Chem. Phys. Lett. 109, 270 (1984)
[3] S.B. Rananavare, V.G.K.M. Pisipati, J.H. Freed, Liquid Crystals 3, 957 (1988)
168
PII_9 Spin-crossover Schiff-base complexes Fe(III). The effect of laser irradiation
I.V. Ovchinnikov1)
, T.A. Ivanova1)
, N.N.Efimov2)
, O.A. Turanova1)
,
G.I. Ivanova1)
, A.A.Sukhanov1)
, L.V. Mingalieva1)
1)
Zavoisky Physical-Technical Institute, Kazan Scientific Center of RAS, 420029,
Sibirsky tract, 10/7, Kazan, Russia
2) NS Kurnakov Institute of General and Inorganic Chemistry of RAS, 119991 GSP_1,
Leninsky Prospekt., 31, Moscow, Russia
Ions Fe (III) (3d5 electronic configuration) may shows a thermally or light induced
transition between the low-spin 2T2 and high-spin
6A1 states (the situation of the spin-
crossover). The investigation of spin state switching by means of relatively weak external
influences is importent from a fundamental scientific and practical points of view.
In this work the spin-variable properties of [Fe(Salten)L] BPh4 with L = Him, Pic
compounds studied by EPR, magnetic susceptibility and under the action of pulsed laser
irradiation in the temperature range 5 – 300 K. The Shiff-base complexes Fe (III) contain the
donor type pentadentate ligand Salten and monodentate ligand L, which complete the
coordination of the ion Fe (III) to 6. X-ray diffraction pattern of the compound [Fe (Salten)
Cl], used as the starting (precursor) in the synthesis of these compounds, corresponds to
literature data; the ions Fe (III) in this complex are in the high-spin state.
It is found that the spin transition is absent in compound with L = Him (S=5/2).
Incomplete spin transition from the high-spin (S = 5/2) to the low-spin (S = 1/2) state takes
place in compound with the L = Pic in the interval (70-300) K. It is manifested in the
integrated intensity of EPR signal decrease from the high-spin complexes of Fe (III) and in
appearance and further increasing (g=4.2) the signal from the low-spin complexes (g1 = 3.024,
g2 = 1.861, g3 = 1.545) with decreasing temperature. It is shown that the ground state of the
low-spin complexes of Fe (III) is |xz> orbital. The wave functions of the ground state and the
ground orbital triplet splitting are defined. Thermodynamic parameters of the spin transition
are determined from analysis of the high-spin signal integrated intensity temperature
dependence and from the magnetic susceptibility data: Tc = 214K, the enthalpy change H =
4.99 kJ K-1
mol-1
, the change in entropy S = 23.3 J K-1
mol-1
, the residual high-spin fraction
of r = 0.11.
A decrease of the integrated intensity of the high-spin EPR signal on average (8-13)%,
(30% in some experiments) is discovered under the action of laser irradiation ( = 532nm) in
both studied compounds. The time to rich stationary state of the signal intensity durind
irradiation and its recovery is ~ 7 min. Effect is absent when =365 nm.
The measurements in time-resolved regime EPR showed: а) at temperature of 5K an
emissive signal formed after the laser flash coincides in form with the integral continuous-
wave EPR spectrum; b) the additional absorption signal corresponding to the position of
signal from the low-spin state arises at temperature 60K; c) the time profiles of the emissive
EPR signals is characterized by two exponential functions describing the fast and slow
kinetics; the time profiles of the absorption EPR signal is characterized by one exponential
function with the rate constant 1.5105 s
-1. Duration of transient processes associated with the
laser pulse action does not exceed the interval between pulses (50 msec).
The possible interpretation of the fast and slow relaxation effects arising under
irradiation in charge transfer metal - ligand range and their temperature dependence are
discussed.
This work was partially supported by RFBR grant 12-03-97090-р_povolzh’e _а.
169
PII_10 Submillimeter EPR spectroscopy of terbium impurity ions in synthetic forsterite
A.A. Konovalov1)
, K.A. Subbotin2)
, V.F. Tarasov1)
, E.V. Zharikov2,3)
1)Kazan Zavoisky Physical-Technical Institute of the Kazan Scientific Center of the Russian
Academy of Sciences, 420029, Sibirskii trakt 10/7, Kazan, Russia 2)
Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991,
Vavilova ul. 38, Moscow, Russia
3)Mendeleev University of Chemical Technology of Russia, 125047, Miusskaya pl. 9,
Moscow, Russia
Synthetic forsterite doped by chromium ions is well known as an active medium for tunable
lasers in the near-infrared range. Rare-earth ions may be also introduced into forsterite during
the crystal growth. The structure and magnetic properties of Ho3+
[1] and Tm3+
[2] impurity
ions in synthetic forsterite were studied earlier. Here we present and discuss some results of
the experimental study of Tb3+
impurity ions in synthetic forsterite. The measurements were
carried out in the frequency range of 100 – 300 GHz on a frequency tunable submillimeter
EPR spectrometer [3]. This spectrometer is based on tunable backward wave oscillators as a
source of the microwave radiation and a wide-band quasi-optic guide. Mg2SiO4:Tb3+
single
crystals were grown from melt with 5 and 10 wt. % of Tb2O3.
We observed four structurally different paramagnetic centers formed by terbium in forsterite.
Two of these centers are the single Tb3+
ions substituting for Mg2+
in M1 and M2 positions of
the crystal lattice. The other two centers are Tb3+
dimer associates. The integral intensity of
resonance transitions belonging to the dimer centers was much higher than that to be expected
for the statistical distribution of the impurity ions in the forsterite host. This means that there
is mechanism favoring the elf-organization of the Tb ions in dimers. We suggest that this
mechanism is connected with the condition of the conservation of the crystal electroneutrality
upon the substitution of bivalent host cations by the trivalent terbium ions. Two Tb3+
ions
substitute three Mg2+
cations to form [Tb3+
-VMg-Tb3+
] (VMg is a vacancy in the magnesium
sublattice) associates the total electrical charge of which equals the charge of three substituted
Mg2+
ions, so that the crystal electroneutrality is conserved.
The directions of principal magnetic axes and parameters of the effective spin Hamiltonian
describing the dependences of electron-nuclear sublevels on the value and direction of the
external magnetic field for two lowest electron levels are presented for all Tb3+
centers.
The work was partially supported by the RFBF grant 12-02-97018.
[1]. Konovalov A.A., Lis D.A., Malkin B.Z., et al.: Appl. Magn. Reson. 28, 267 (2005)
[2]. Konovalov A.A, Lis D.A., Subbotin K.A., et al.: Appl. Magn. Reson., 30, 673 (2006)
[3]. V. F. Tarasov, G. S. Shakurov, Appl. Magn. Reson. 2, 571 (1991)
170
PII_11 Electron-nuclear energy levels anticrossings in Al2O3:V3+
G.S.Shakurov
Kazan Physical Technical Institute, 420029, Sibirsky trakt 10/7, Kazan, Russia.
Quantum tunneling of magnetization (QTM) is intensively studied in the recent time because
of its promising application in modern technologies. The necessary condition of QTM is the
existence of the energy levels anticrossings. Although the main attention attracts single-
molecule magnets, the crystals with rear earth and transition metal ions are the model systems
for magnetization dynamic investigation. Usually the impurity ion has electron-nuclear
sublevels of the ground doublet where avoided level crossing takes place. In the present work
we studied excited level anticrossings of V3+
ion in corundum using tunable high frequency
EPR spectroscopy. The spectroscopic properties of V3+
(S=1, I=7/2) in corundum (α-Al2O3)
are well-studied. The excited doublet removed from ground singlet at 248 GHz. Early the
high frequency EPR measurements where singlet-doublet transitions between electron-nuclear
sublevels were observed gave possibility to measure small splitting of the doublet
(2E=1.6±0.6 GHz) [1]. It means that energy gaps should be between crossing sublevels with
Δm=0 (m-is nuclear spin projection). Besides because of proximity of singlet the high-order
terms in the hyperfine interaction also should lead to anticrossings in the region Δm=2 [2].
Indeed the measurements show that EPR spectra in these regions have peculiarities. In Fig.1
EPR spectra of V3+
in corundum at frequencies in region crossing (247.47 GHz, 248.05 GHz)
and anticrossing (247.87 GHz, Δm=0) are shown. To compare the intensity spectra taken on
the different frequencies, EPR spectrum of Ho3+
ions in sheelite was used.
0,0 0,5 1,0 1,5 2,0
B, kG
247.47
247.83
247.87
247.9
248.05
, GHz
Fig.1. EPR spectra of Al2O3:V
3+ taken at frequencies in the region crossings and anticrossings (on the
left) and two lines of hyperfine structure of Ho3+ in CaWO4 added as intensity standard. (on the right).
[1] E.A.Vinogradov et al. JETP letters. 4, 252 (1966)
[2] G.S.Shakurov et al. Appl. Magn. Reson. 28 251 (2005)
171
PII_12 EPR of Gd3+
in micro- and nanoscale LaF3 particles
A.M. Sabitova, E.M. Alakshin, R.R. Gazizulin, D.G. Zverev, A.V. Klochkov, S.L. Korableva,
A.A. Rodionov, K.R. Safiullin, M.S. Tagirov
Kazan (Volga region) Federal University, 420008, Kremlevskaya 18, Kazan, Russia
The X-band electron paramagnetic resonance of Gd3+
ion doped in the diamagnetic
LaF3 nanoparticles at a room temperature was investigated. The four nanosized LaF3:Gd3+
samples 1, 2, 3 and 4 were synthesized using different time of hydrothermal reaction [1,2]. In
typical synthesis, lanthanum oxide is dissolved in nitric acid solution. Then, after filtering,
NaF (F:La with 0,5% Gd = 3:1) was added into the above solution under violent stirring. The
pH of the suspension was adjusted by ammonia to about 4.0-5.0 value. After stirring for 20
min, the suspension was placed in the microwave oven (650 W) for the further hydrothermal
reaction. The suspension was heated by microwave irradiation at 70% of the maximum power
under refluxing for 0, 20, 40, and 420 min (samples numbers 1, 2, 3 and 4 respectively). The
resulting product was collected by centrifugation and washed several times in deionized
water. The X-ray experiments showed high crystallinity of synthesized samples. The micron-
sized sample was prepared by milling of a single crystal LaF3:Gd3+
.
The X-band EPR of Gd3+
ion has been observed in LaF3:Gd3+
powders at the room
temperature. The EPR spectra (Fig.1) were obtained at Bruker ESP-300 spectrometer.
Influence of the sample size and hydrothermal reaction duration on obtained spectra is
observed. Current EPR studies on doped LaF3 powders will be peported.
Fig.1 EPR spectra of nano- and micro- sized powders LaF3:Gd3+
.
[1]L.Ma et al., JETP Lett., 86, 416 (2007).
[2] E.M. Alakshin et al., J. Low. Temp. Phys., 162, 645 (2011).
172
PII_13 EPR of Gd157
in CaWO4. The influence of the implicit and
explicit contributions on the parameters b20, P2
0.
A.D. Gorlov1)
, I.N. Kurkin2)
1) Ural Federal University, INS, Lenina 51, 620083 Ekaterinburg, Russia
2) Kazan Federal University, Institute of Physics, Kremlevskaya 18, 420008, Kazan, Russia
E - mail: Anatoliy.Gorlov @ usu.ru
The EPR spectrums (the allowed and forbidden transitions) of the odd isotopes Gd3+
in the crystals CaWO4 were investigated in the temperature range T=1.8K, 100-298K. It was
revealed that the second ranks parameters of the spin-Hamiltonian defining the ground-state
splitting (b20)
and nuclear quadrupole interaction (P2
0) decrease synchronously with
increasing of temperature. Set of b20 and P2
0 (in MHz) parameters are presented in Table. Our
resalts for 4.2K and 298K are good agreement with those of Harvey and Kiefte [1].
T(K) gx=gy gz b2
0 b40 b4
4 P20 b2
0(calc.) b20
1.8 1.992(1) 1.992(1) -2757(1) -71.9(5) -437(4) -63.4(1) -2766(20) -9(21)
4.2 1.992(1) 1.992(1) -2757(1) -71.7(5) -437.7(16) -63.3(4) -2766(20) -9(21)
105 1.9915(6) 1.9915(7) -2738.6(5) -71.4(3) -434.3(15) -62.6(4) -2779(20) 40(21)
187 1.9916(5) 1.9914(5) -2716.7(5) -70.2(3) -429.3(14) -62.5(4) -2800(20) 83(21)
298 1.9918(8) 1.9916(5) -2679.7(5) -68.4(3) -420.3(16) -62.2(5) -2841(20) 161(21)
b64=13(11), b4
6 =0(2), Ax=Ay=16.2(2), Az=16.3(3) for Gd157.
The EPR measurements were carried out on a Bruker EMX X-band spectrometer. The
simulations of the hyperfine structure (HFS) of EPR signals Gd157
for the various orientations
of external magnetic field show that observed HFS is dependent on the signs of b20, Ai (i=x,z)
and P20. The b2
0 to P2
0 ratio is approximately constant (44.3(3)).
Our estimation of b20 (superposition model D. J. Newman with the intrinsic
parameters [2]) and lattice constants [3] for different T show that the implicit effect
(expansion lattice from T) manifests itself in changing of b20(1.8K) by (-2.7%), while the
explicit effect gives 5.8%. In this model we have taken into account only the radial
displacement of the ligands. The ligands distance were determined as ri = r0+(rGd – rCa)/2,
where r0-distanse for CaWO4lattice, rCa and rGd are the ions radiuses in 8-fold environment
[4].
[1] J. S. M. Harvey and H. Kiefte, Can. J. Phys., 49, 995 (1974).
[2] L. I. Levin and A. D. Gorlov, J. Phys.: Condens. Matter. 4 (4), 1981 (1992).
[3] A. Senyshyn et al., J. Appl. Cryst. 44, 319 (2011).
[4] R.D. Shannon, Acta Cryst. A32, 751 (1976).
173
PII_14 Clusters of rare-earth ions in the mixed fluoride crystals studied by EPR
L.K. Aminov, M.R. Gafurov, I.N. Kurkin, A.A.Rodionov
Institute of Physics, Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russia
Mixed fluoride crystals (MeF2)1-x(RF3)x (Me = Ca, Sr, Ba; R = Y, La, Lu and other
lanthanides) are the single-phase crystals with a cubic lattice structure of CaF2 type in a wide
concentration range (0 x 0.4). At low х 10-4
– 10-3
R3+
ions substitute Me2+
as “single
impurity centers”. In this case the compensator F- ions occupy either the interstitial lattice
sites close to R3+
(local compensation) or the positions far apart from the lanthanides. With
the increase of the trifluoride concentration a probability of the formation of extensive
structural defects which include a number of R3+
cations and F- anions in interstitial positions
is growing up.
To minimize the influence of strong interactions between the rare-earth ions within the
clusters and, therefore, to simplify the analysis, the binary “solutions”
(MeF2)1-x-y(ReF3)x(RF3)y with the diamagnetic R3+
and low concentrations x of the
paramagnetic rare-earth Re3+
are often studied with the electron paramagnetic resonance
(EPR) methods. Kazanskii [1] examined a series of different binary “solutions” and
concluded that in all of them the only clusters R6F36 (37) with the cuboctahedral symmetry
were formed. The clusterization starts from the very low total concentrations of x + y 10-3
.
However, the proposed clusterization model is not universal. We found no La6F36 but
linear clusters La3+
- F- - Yb
3+ - F
- elongated along the trigonal axis in
(BaF2)1-x-y(YbF3)x(LaF3)y [2]. Some EPR lines in (BaF2)1-x-y(CeF3)x(LaF3)y were attributed to
the formation of La6F36 clusters wherein one of the La3+
ions was substituted by Ce3+
[3]. But
the same EPR pattern was detected in a pure ceric material ( y = 0) with the x increase [4].
Beside that the same EPR lines were obtained in the earlier works in Na+ doped CaF2:Ce
3+
crystals [5].
These facts forced us to continue the study of the clusterization of the fluoride
inclusions.
The results for (BaF2)1-x(CeF3)x x = 0; 0.001; 0.002; 0.005; 0.01; 0.02 are reported.
“New tetragonal centers” appear starting from x = 0.002. Their intensity is maximal at
x = 0.01 and decreases at higher x.
In very similar system (CaF2)1-x-y(CeF3)x(YF3)y with x = 0.001 and y in the range 0-
0.02 the formation of the new tetragonal centers begins already from y = 0.001. Its origin is
apparently the same as in the BaF2 based mixed crystals.
EPR spectra were registered on Bruker ESP 300 spectrometer in continuous wave
mode at T = 15 K in the magnetic field range of (20-1400) mT.
[1] S.A. Kazanskii, JETP 62, 727 (1985) [ZhETF 89, 1258 (1985)].
[2] L.K. Aminov, R.Yu. Abdulsabirov, M.R. Gafurov, S.L. Korableva, I.N.Kurkin, S.P.
Kurzin, R.M. Rakhmatullin, A.G. Ziganshin, Appl. Magn. Reson. 28, 41 (2005).
[3] L. K. Aminov, I. N. Kurkin, S. P. Kurzin, I. A. Gromov, G. V. Mamin, R. M.
Rakhmatullin, Phys. Solid State 49, 2086 (2007) [FTT 49, 1990 (2007)].
[4] L. K. Aminov, I. N. Kurkin, Phys. Solid State 55, 123 (2013) [FTT 55, 108 (2013)].
[5] S.D.McLaughlan, Phys. Rev. 160, 287 (1967).
174
PII_15 Transient nutations in Nd-doped CaWO4 crystal
E.I. Baibekov1)
, M.R. Gafurov1)
, D.G. Zverev1)
, I.N. Kurkin1)
, B. Barbara2)
1)
Kazan Federal University, 420008 Kazan, Russian Federation 2)
Institut Néel, CNRS and Université Joseph Fourier, BP166, 38042 Grenoble Cedex 9,
France
As was proposed recently, lanthanide ions in the crystal field background can function
as multilevel solid-state qubits driven by the resonant field of a microwave (MW) cavity [1].
Spin-orbit, crystal field and hyperfine interactions, acting simultaneously, cause the
entanglement of the electron spin, its angular momentum and the nuclear spin of the
lanthanide ion, resulting in a complex multilevel energy spectrum within which a selective
addressing is possible [2]. The present study focuses on a series of four Nd:CaWO4 single
crystals with different neodymium concentrations (C = 0.0016÷0.58 at. %). These crystals
were first experimentally studied by means of pulsed electron paramagnetic resonance using
X-band (9.8 GHz) Bruker Elexsys E680 spectrometer at temperatures near 6 K. Transient
nutations (TN) between the Nd3+
states were detected for several Nd isotopes (with and
without nuclear spin) and at different MW power levels. In all cases the TN decay times TN
were inversely proportional to the MW field strength. The substantial decrease of TN was
observed for two samples with large Nd concentrations (C > 0.1 at. %). At lower
concentrations, TN was almost invariable with C and did not depend on the presence of the
nuclear spin.
The interpretation of the experimental data was carried out within the framework of
microscopic theory of dipolar relaxation in the presence of MW field [3]. In our calculations,
we distinguished between the relaxational and dephasing contributions to TN decay rate 1
TN .
The former involved the magnetic dipole coupling of Nd3+
ion with other neodymium ions
randomly distributed within the crystal lattice. A certain modification of the theory [3] was
developed to calculate the dipolar part in the case of tetragonal symmetry of the crystal
background. The dephasing contribution originated from the distribution of MW field strength
over the crystal sample which is known to give a slow polynomial-type decay of TN [4] and
is independent of either С or the presence of the nuclear spin. That corroborated the observed
decay pattern in the first two samples with small C. For larger Nd concentrations, the dipolar
contribution prevailed and gave the exponential decay with 1
TN C.
The results demonstrate the possibility of spin manipulations in Nd:CaWO4 single
crystal and indicate its future prospects for quantum information processing. We believe that
the proposed calculation scheme involving the separation of the relaxational and dephasing
mechanisms of TN decay would facilitate the search for the most promising solid-state qubits
based on lanthanide or transition metal ions.
E.I.B. acknowledges the support of RFBR (grant no. 12-02-31336) and of Dynasty
Foundation.
[1] S. Bertaina, S. Gambarelli, A. Tkachuk, I. N. Kurkin, B. Malkin, A. Stepanov, B. Barbara,
Nature Nanotechnol. 2, 39 (2007).
[2] S. Bertaina, J.H. Shim, S. Gambarelli, B. Z. Malkin, B. Barbara, Phys. Rev. Lett. 103,
226402 (2009).
[3] E. I. Baibekov, JETP Lett. 93, 292 (2011).
[4] E. I. Baibekov, I. N. Kurkin, M. R. Gafurov, B. Endeward, R. M. Rakhmatullin, G. V.
Mamin, J. Magn. Res. 209, 61 (2011).
175
PII_16 Hyperfine structure in the infrared absorption spectra of CaWO4:Ho3+
E.P. Chukalina, M.N. Popova
Institute of Spectroscopy, Russian Academy of Science, 142190, 5 Fizicheskaya st., Troitsk, Moscow,
Russian Federation
Calcium tungstate (CaWO4) doped with rare earths (RE) is used as a scintillator and laser
material. It crystallizes in the tetragonal scheelite structure (space group C4h6). The main
feature of this structure is the presence of isolated WO4 tetrahedra. Each Ca2+
ion shares
corners with eight adjacent WO4 tetrahedra. The trivalent rare earth ions substitute for Ca2+
,
forming centers with, mainly, nonlocal charge compensation, so that their point symmetry is
S4. Earlier, the energy levels of the ground term 5I of the Ho3+ ion in CaWO4 were investigated by
absorption and fluorescence spectra measurements and crystal-field calculations have been done [1].
But the hyperfine structure (HFS) in the spectra of Ho:CaWO4 was not observed in this work
performed at rather low spectral resolution. The study of the HFS is important in connection
with new applications of the rare-earth-doped crystals in quantum information storage and
processing devices, based on the three-level Λ-systems built on the hyperfine levels of the RE
ion.
We have performed the high resolution optical spectroscopic study of the f-f transitions of
Ho3+ in CaWO4. Polarized absorption spectra of the single crystal CaWO4:Ho3+ (0.05 %) were
measured in the broad temperature
(5-300 К) and spectral (4000-
10000 cm-1
) ranges using a
Fourier-transform spectrometer
Bruker IFS 125HR and a closed-
cycle optical cryostat Cryomech
ST430. The spectral regions of 5I8→
5I7,6 transitions in Ho
3+ ion
were investigated with the spectral
resolution up to 0.01°cm-1
. We
have observed well-resolved HFS
of spectral lines caused by the
hyperfine interaction that involves
the nuclear magnetic dipole and
electric quadrupole contributions.
Some examples of hyperfine
patterns are shown in Fig. 1.
This work was supported by the Russian Foundation for Basic Research (grant No 13-02-
01091).
[1] D.E. Wortman and D. Sanders, Journal of Chem. Phys. 53, 1247 (1970).
Fig. 1 Absorption lines corresponding to the doublet-doublet and
doublet-singlet transitions in the region of the 5I6 optical multiplet.
176
PII_17 Size-dependent crystal field distortions in yttrium doped
nanocrystalline ceria
R. M. Rakhmatullin1)
, L. K. Aminov1)
, I. N. Kurkin1)
, R. Böttcher2)
, A. Pöppl2)
, S. Sen3)
1)
MRS Laboratory, Kazan State University, Kremlevskaya 18, 420008 Kazan, Russia 2)
Faculty of Physics and Earth Sciences, University of Leipzig, Linnéstr. 5, D-04103 Leipzig,
Germany 3)
Department of Chemical Engineering and Materials Science, University of California at
Davis, California 95616, USA
E-mail: [email protected]
Ceria (CeO2) is an important material for many technological applications such as solid oxide
fuel cells (SOFC), solar cells, three way catalysts, etc. [1-3]. These applications are based on
the oxygen storage capacity (OSC) of ceria – the ability to store oxygen under oxidizing
conditions and to release it under reducing conditions. In pure ceria this process is associated
with the change in the oxidation state of cerium between Ce3+
and Ce4+
and formation of
oxygen vacancies in the lattice structure by loss of oxygen and/or its electrons [1]. Doping
with trivalent rare earth ions introduce additional oxygen vacancies in ceria and increases
OSC of ceria. In recent years many efforts focus on the study of nanocrystalline ceria that
have the promise to display OSC significantly higher and more stable than that characteristic
of their micro-crystalline counterparts. This feature was supposed to be related to the
increased surface contribution though unambiguous and clear understanding of their local
structure remains lacking to date.
In this work the size-dependent changes in EPR spectra of Gd3+
ions in nanocrystalline ceria
(with grain sizes of 10 and 600 nm) doped with yttrium (0.5, 1 and 5 at.%) have been
investigated. The observed spectra were fitted by the superposition of contributions having
cubic and trigonal symmetry. The spectra of the bulk sample (600 nm grain size) with the
minimal concentration of yttrium (0.5 at%) is about of cubic symmetry; the trigonal
contribution becomes notable at 1 at% of yttrium and prevails at 5 at% concentration.
The spectra of the samples with fine grains (10 nm) reveal two types of trigonal centers,
which contributions to the spectra differ for different concentration of yttrium. These two
types of centers are referred to interior and surface parts of the crystallites. Our findings point
out clearly at the local distortions in the lattice structure when the size of grains decreases
down to nanometer scales.
For samples with 10 nm grains the contribution of the broad line with g – values close to that
of superoxide radicals was found.
[1] A. Trovarelli, Ed., Catalysis by Ceria and Related Materials (Imperial College Press,
London, 2002).
[2] E.P. Murray, T. Tsai, S.A. Barnett, Nature 400, 649-651 (1999)
[3] A. Corma, P. Atienzar, H. Garcia, J.Y. Chane-Ching, Nature materials , 3, 394 - 397
(2004)
177
PII_18 An X- and Q-band Fe3+
EPR Study of Nanoparticles of
Magnetic Semiconductor Zn1-xFexO
Sushil K. Misra,1)
S. I. Andronenko,2)
A. Thurber,3)
A. Punnoose,3)
A. Nalepa4)
1)
Physics Department, Concordia University, Montreal, QC, H3G 1M8, Canada 2)
Physics Institute, Kazan Federal University, Kazan, 420008, Russian Federation 3)
Department of Physics, Boise State University, Boise, ID 83725-1570, U.S.A 4)
Max Planck Institute for bioinorganic chemistry, Mülheim um der Ruhr, Germany
EPR studies on two types of nanoparticles of ZnO, NL and QJ, prepared using similar
chemical hydrolysis methods, in diethylene glycol, and in denatured ethanol solutions,
respectively, doped with 0.1 – 10 % Fe3+
, were carried out at X-band (9.5 GHz) at 77 K and at
Q-band (34 GHz) at 10, 80, 295 K. To interpret the experimental results, EPR spectra were
simulated by exact diagonalization of the spin-Hamiltonian matrix, in order to identify the
presence of Fe ions at different magnetically active sites in these samples. The simulation of
EPR spectra for NL samples revealed that they contained (i) Fe3+
ions, which substituted for
Zn ions, exhibiting trigonal Fe3+
EPR spectrum in crystalline ZnO, the zero-field splitting
(ZFS) parameter for which has a large distribution over the sample due to oxygen vacancies
in the second coordination sphere; (ii) Fe3+
ions characterized by very small ZFS; and (iii)
ferromagnetically (FM) ordered Fe ions in samples with concentration of Fe more than 1%.
ZnO nanoparticles. The EPR spectra for QJ samples are very different from those for NL
samples, clearly exhibiting Fe3+
EPR spectra belonging to localized ions. The ferromagnetism
and EPR spectra are found to vary strongly with differences in the surface morphology of
nanoparticles.
The main conclusions of our EPR investigations of ZnO nanoparticles are as follows:
(i) The observed EPR spectra provide clear evidence for the presence of both
paramagnetic Fe3+
ions exhibiting sharp lines, as well as ferromagnetically coupled Fe ions
producing a single broad signal. Both the paramagnetic Fe3+
ions and the ferromagnetic
components are present in NL samples with Fe concentration of more than 2.5%.
(ii) The EPR spectrum for localized Fe3+
ions has been successfully interpreted here
by taking into account the Gaussian distribution of the zfs ( 0
2b ) parameter. Both sets of EPR
signals, HS1 and HS2, became more intense with increasing Fe concentration.
(iii) The paramagnetic fraction of the doped ions does not contribute to the
ferromagnetic coupling. This explains the smaller magnetic moment observed in NL samples.
QJ samples, on the other hand, only exhibit FM resonance signals, suggesting that all the
doped Fe ions in them are magnetically coupled. This accounts for their stronger
ferromagnetism.
Fig. 1. The observed Q-band
EPR spectrum at 10 K and
simulated Fe3+
EPR spectra (NL
samples) constituting it in
nanoparticles of ZnO, doped
with 0.1% Fe
178
PII_19 High-Frequency EPR of Er3+
ions in YAG
H.R. Asatryan1)
, G.S. Shakurov2)
1)
Ioffe Physical-Technical Institute, 194021, Politekhnicheskaya 26, St-Petersburg, Russia 2)
Kazan Physical Technical Institute, 420029, Sibirsky trakt 10/7, Kazan, Russia.
Yttrium-aluminum garnet Y3Al5O12 (YAG) doped with Er3+
ions was studied early by
electron paramagnetic resonance (EPR) at X-band [1, 2]. The Er3+
ion localization, g-values
and hyperfine constants of the ground and first excited level were determined. It should be
noted that the excited doublet population was carried out by means of thermal method.
We undertaken the broad-band (37-850 GHz) EPR study of the two crystals of YAG with the
Er concentrations 0.1% and 10 % at the temperature 4.2 K. Magnetic field up to 9 kG was
produced by the usual electromagnet.
In the frequency region 37-150 GHz we observed EPR spectrum of the ground doublet
of Er3+
ions. The inter doublet resonance transitions were registered between 570 GHz and
720 GHz. Energy distance between the ground and excited doublets (~24 cm-1
) was known
from the optical measurements. The angular diagrams and field-frequency dependencies of
the inter doublet transitions gave possibility to refine the known spectral parameters.
Although lines width of the intra doublet transitions for sample with 0.1% concentrations was
small and hyperfine structure (HFS) was resolved, EPR lines of inter doublet transitions were
strongly broadened. Similar effect of the line width increasing was observed for 10 %
concentration sample. Besides of the well-known Er3+
center we observed week EPR signals
from the new center for both concentrations. The Zero-Field-Splitting (ZFS) of the new center
was lesser than the known one and HFS was not resolved. Moreover the small signal to noise
ratio and overlapping EPR lines of the new and well-known centers not allowed measuring its
angular diagrams. In the Fig.1 EPR the spectrum of inter doublet transitions of both Er centers
is presented.
0 2 4 6 8
B (kG)
21
Fig.1. EPR spectrum of YAG:Er3+ (0.1%). Frequency 618 GHz. B || [110]. 1-new center, 2-well-
known center.
The origin of the new Er center and the peculiarities intra doublet transitions of the well-
known center are discussed in the report.
[1] M. Ball et al J. Appl. Phys. 32 Suppl. 267S (1961)
[2] H.R. Asatryan at al. Soviet Phys. Sol. State. 33 976 (1991)
179
PII_20 Nano-Hydroxyapatite as studied by multi-frequency (9 and 94 GHz)
EPR and ENDOR
T.B. Biktagirov1)
, M.R. Gafurov1)
, G.V. Mamin1)
, S.B. Orlinskii1)
, A.A.Rodionov1)
,
B.V. Yavkin1)
, E.S. Klimashina2)
, V.I. Putlayev2)
1)
Institute of Physics, Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russia 2)
Department of Chemistry, Moscow State University, 119992, Moscow, Russia
Initial interest to the nanosized hydroxyapatite Ca9Pb(PO4)6(OH)2 (nano-HAp) is
governed by the search for reliable prognostic markers to trace the atherosclerotic plaque
development at the earlier stages of atherosclerosis. We have started from the tissues of aorta
walls of male patients and synthesized nano-HAp as model systems for the calcified tissues.
We have shown that exploiting the increased sensitivity and resolution of the high-frequency
(HF) electron paramagnetic resonance (EPR) the spectroscopic and relaxation characteristics
of manganese ions (Mn2+
) and of radiation induced carbonate radicals could be used to trace
the atherosclerosis development [1-3].
We have spread our studies onto the investigations of different nano-HAp samples by
means of X- (10 GHz) and W- band (94 GHz) EPR and double resonance (ENDOR) pulsed
techniques. It is demonstrated that during the wet synthesis process nitrate anions from the
by-products could incorporate into the structure of the hydroxyapatite structure. Thermal,
relaxation and spectroscopic characteristics of the observed stable NO32-
radical and its
structure which slightly differ from those obtained in bulk materials (Fig.1) are discussed in
this work. From ENDOR results it is suggested that the nitrate anions are embedded into the
OH channels of the hydroxyapatite structure. With the increase of the carbonization level
from 0 to 2% the concentration of the nitrogen-concerning radicals vanishes drastically [4].
To our knowledge, it is the first experimental support of the carbonate-nitrate interchange.
Study of intentionally incorporated Pb2+
ions show that they are at least distributed among the
Ca(1) and Ca(2) positions in nano-HAp structure [3, 5] in contradiction with the common
believe.
3,335 3,340 3,345 3,350 3,355 3,360 3,365
2Apar
2A
W - band
ES
E A
mp
litu
de
(a
.u.)
B0 (T)
exp
sim
g
gpar
[1] V. A. Abdul’yanov et al., Stationary and high-frequency pulsed electron paramagnetic
resonance of a calcified atherosclerotic plaque. JETP Lett., 2008, 88, 69.
[2] N.I.Silkin et al., 2011, Patent RU 2468368.
[3] M.R. Gafurov et al. Atherosclerotic plaque and hydroxyapatite nanostructures studied
by high-frequency EPR, Magn. Reson. Solids, 2013, 15, 13102.
[4] N.I.Silkin et al., 2011, Patent RU 2465573.
[5] B. V. Yavkin et al., Pb3+
radiation defects in Ca9Pb(PO4)6(OH)2 hydroxyapatite
nanoparticles studied by high-field (W-band) EPR and ENDOR, Phys. Chem. Chem.
Phys., 2012, 14, 2246.
Fig. 1. Electron Spin Echo detected EPR
spectrum of nano-HAp after X-ray irradiation at
94 GHz at T = 297 K (exp) along with the
simulation curve (sim). Arrows show the
components of g- and A- tensors of NO32- radical.
180
PII_21 Impact of random lattice deformations on low-temperature spectral
and magnetic properties of Tb2Ti2O7 pyrochlore
V.V. Klekovkina, B.Z. Malkin
Kazan Federal University, 420008, 18 Kremlevskaya St., Kazan, Russia
The origin of spin-liquid behavior of Tb2Ti2O7 at low temperatures is still misunderstood.
Four magnetically non-equivalent terbium sublattices form a corner-sharing tetrahedral
network with the cubic symmetry. The lower fragment of the energy spectrum of the Tb3+
ions in the crystal fields of the D3d symmetry contains two non-Kramers doublets with a gap
of 1.5 meV and g-factors g||>10. According to calculations within the random phase
approximation, Tb2Ti2O7 should undergo antiferromagnetic phase transition at T1 K. At the
same time, anomalous softening of the crystal lattice indicate that a cooperative Jahn-Teller
transition should occur at T ~0.1 K. However, magnetic neutron scattering data and high-
resolution X-ray experiments do not show magnetic or structural phase transitions in
Tb2Ti2O7 single crystals down to ~0.07 K. Explanations of the absence of long-range
magnetic ordering are based on assumptions of quantum spin fluctuations which suppress
antiferromagnetic exchange interactions (the so called Quantum Spin Ice model [1]) or of the
static tetragonal lattice distortion that brings about the single ion singlet ground state [2].
One more important experimental fact is the sample dependence of the specific heat
anomalies, magnetic susceptibility and neutron scattering data at low temperatures. Also
breaking of selection rules in Raman and IR spectra and multi-center structure of optical
spectra indicate on presence of lattice defects which can be associated with the
nonstoichiometry of Tb2+xTi2-xO7+y. Local lattice deformations induced by defects and
corresponding random low-symmetry crystal fields affecting the Tb3+
ions can modify
essentially different physical properties of Tb2Ti2O7 even in a case of rather small defect
concentration due to the strong 4f electron-strain interaction in this system.
In the present work, we performed a theoretical study of the inelastic neutron scattering,
temperature dependences of the specific heat, elastic constants and magnetic dc-susceptibility
of Tb2Ti2O7 with taking into account random deformations induced by point lattice defects
(centers of compression or dilatation). The measurable quantities were calculated using
averaging over the generalized distribution function for local strains produced by point
defects in the elastic continuum [3] with the width determined from fitting the shape of the
neutron inelastic scattering intensity peaking at the transferred energies of 0.16-0.20 meV.
Linear coupling constants in the Hamiltonian of the electron-deformation interaction of the
Tb3+
ions were calculated within the framework of the exchange charge model and checked
by the analysis of the magnetoelastic effects.
The assumption about presence of random lattice deformations of an order of ~ 4⋅10-4
allows successful description of spectral, magnetic and elastic properties of Tb2Ti2O7 at low
temperatures when the corresponding shifts and splittings of the crystal field levels of the
Tb3+
ions are comparable to thermal excitations. The results obtained confirm the significant
role of lattice defects in destroying the magnetic ordering and structural phase transition in the
terbium titanate.
VVK acknowledges the support from Ministry of Education and Science of Russian
Federation (contract No. 14.132.21.1413).
[1] H.R. Molavian, M.J.P. Gingras, B. Canals, Phys. Rev. Lett. 98, 157204 (2007)
[2] P. Bonville et al. Phys. Rev. B 84, 184409 (2011).
[3] B.Z. Malkin et al. Phys. Rev. B 86, 134110 (2012).
181
PII_22 Spectral and magnetic properties of orthorhombic oxides
SrR2O4 (R=Dy, Er, Ho, Yb)
D. F. Nabiullin, B. Z. Malkin
Institute of physics, Kazan Federal University, Kazan, Russian Federation
The orthorhombic crystal lattice of oxides SrR2O4 (R=Dy, Er, Ho, Yb) with the space group
Pnam (62, D2h16
) contains rare earth (RE) ions in two inequivalent positions. Both sites, S1
and S2, with the point symmetry Cs are surrounded by six oxygen ions. The identical RE ions
form chains connected in the zigzag manner ladders along the crystallographic c-axis and the
honeycomb network (edge sharing hexagons) in the ab plane [1]. According to neutron
scattering data and heat capacity measurements, these systems exhibit a large variety of
unconventional magnetic properties including the long-range antiferromagnetic ordering in
SrEr2O4 (TN=0.75 K) and SrYb2O4 (TN=0.95 K) that involves only half of RE ions and may
coexist with short-range incommensurate ordering, while there are only short-range
correlations between magnetic moments of RE ions in SrHo2O4 [2] and SrDy2O4 at least down
to 20 mK [3]. To interpret specific magnetic properties of these compounds, it is necessary to
know spectral properties of RE ions. In the present work, we computed energy spectra and
static magnetic susceptibilities of RE ions in oxides SrR2O4 within the framework of the
crystal-field (CF) theory by making use of the exchange charge model to obtain initial values
of CF parameters and the mean field approximation to analyze the magnetization.
Temperature dependences of the susceptibility and field and temperature dependences of the
magnetization were calculated at temperatures 1-400 K and external magnetic fields over 0.1
T with taking into account magnetic dipole-dipole interactions and orbital reduction factors.
The results of calculations agree at least qualitatively with the experimental data available
from literature [4,5].
[1] H. Karunadasa, Q. Huang, B.G. Ueland, J.W. Lynn, P. Schiffer, K.A. Regan, R.J. Cava,
Phys. Rev. B 71, 144414 (2005)
[2] O. Young, A.R. Wildes, P. Manuel, B. Ouladdiaf, D.D. Khalyavin, G. Balakrishnan, O.A.
Peterenko, cond-mat. arXiv:1306.1762 (2013).
[3] T.H. Cheffings, M.R. Lees, G. Balakrishnan, O.A. Petrenko, J. Phys.: Condens. Matter 25,
256001 (2013).
[4] T.J. Hayes, O. Young, G. Balakrishnan, O.A. Petrenko, J. Phys. Soc. Japan 81, 024708
(2012).
[5] D.L. Quintero-Castro, B. Lake, M. Reehuis, A. Niazi, H. Ryll, A.T.M.N. Islam, T.
Fennell, S.A.J. Kimber, B. Klemke, J. Ollivier, V.G. Sakai, P.P. Deen, H. Mutka, Phys. Rev.
B 86, 064203 (2012).
182
PII_23 Studies of natural bornite by nuclear-resonance spectroscopy
R.R. Gainov1,2)
, V.V. Klekovkina1)
, A.V. Dooglav1)
, F.G. Vagizov1)
,
V.A. Golovanevskiy3)
, I.N. Pen’kov1)
, G. Klingelhöfer2)
, V. Ksenofontov2)
1)Kazan Federal University, 420008, 18 Kremlevskaya Str., Kazan, Russian Federation
2)Johannes Gutenberg University of Mainz, D-55099, 9 Staudingerweg, Mainz, Germany
3)Curtin University, 6008, Kent Street, Bentley, Perth, Australia
Ternary chalcogenide materials have attracted attention due to their important physical-
chemical properties and promising potential applications in solar power engineering and
spintronics [1]. The electronic features of these compounds in many cases cannot be studied
effectively by conventional materials characterisation tools and instead can be detected by
several microscopic methods only. Nuclear-resonance spectroscopy methods, including
nuclear gamma resonance (NGR or Mössbauer effect), nuclear magnetic resonance (NMR)
and nuclear quadrupole resonance (NQR) are often very suitable in such cases. One of the
major open questions concerning CuxFeyS(Se,Te)z materials is related to the uncertain
attribution of the metal valence states. Another important question concerns the structural
Cu/Fe distribution over the crystal lattice. In fact, these aspects determine a rich variety of the
electronic and magnetic properties of CuxFeyS(Se,Te)z materials.
Bornite Cu5FeS4 is known as extremely complicated specimen of CuxFeySz system.
Generally, bornite has “low”, “intermediate” and “high” temperature forms, with only the
“low”-T form (T < 444 K) occurring naturally [2]. The “low”-T bornite has an orthorhombic
cell (a, b, c = 10.950, 21.862, 10.950 Å) with two subcells [2]: antifluorite-type units,
containing 8 metal atoms located at tetrahedral sites, and sphalerite-like units, consisting of 4
metal atoms and 4 vacancies located also at the tetrahedral sites. Interestingly, both magnetic
and Mössbauer studies show a magnetic phase transition to an antiferromagnetic state at TN =
67.5 K and suggest the fluctuating valences between Fe3+
↔Fe2+
[3]. At the same time, it was
noted that natural bornite samples often have the nonstoichiometric composition and their
experimental results are affected by the metal/sulfur and Cu/Fe ratio. Indeed, as shown earlier
the Fe magnetic moment found for different natural bornite samples, which depends on the Fe
valence, is characterised by a wide range [3]. In this context, it appears expedient to carry out
complementary studies of bornite samples using two nuclear-resonance methods: NMR and
Mössbauer spectroscopy on copper and iron nuclei-probes.
Our preliminary low-temperature studies of natural bornite confirm some previous
results and imply new details. In fact, the low-temperature copper NMR measurements reveal
very complicated spectrum, consisting of several groups of lines. The result obtained supports
the antiferromagnetic state due to the magnetic ion of iron and proves the crystal-chemical
nonequivalence of tetrahedral sites for metal atoms. At the same time, there are aspects which
require further studies for clarification. As an example, the exact nature of the
antiferromagnetic ordering is not clear up to now. This question and several others can be
resolved satisfactorily using stoichiometric samples (natural or, more desirable, synthetic).
This report will present preliminary results of the experimental studies of natural bornite
Cu5FeS4 and a discussion of its electronic and magnetic properties at low temperatures.
This work is partly supported by RFBR grant under No.12-02-31282 (mol_a).
[1] Fuertes Marron D et al., et al. Sol. Energy Mater. Sol. Cells, v.94, p.1912 (2010)
[2] Koto K., Morimoto N., Acta Crystallogr. Sect. B, v.31, p.2268 (1975)
[3] Jagadeesh M.S. et al., Phys. Rev. B, v.23, p.2350 (1981)
183
PII_24 Optical and EPR spectroscopy of NicMg1-cO solid solutions
N. Mironova-Ulmane1)
, V. Skvortsova1)
, M.G. Brik2)
, I.Sildos2)
, T. Kärner2)
1)
Institute of Solid State Physics, University of Latvia, Kengaraga street 8, LV-1063, Riga,
Latvia
2) Institute of Physics, University of Tartu, Riia 142, Tartu 51014, Estonia
E-mail: [email protected] , [email protected]
NicMg1-cO solid solution is an excellent model system to study magnetic ions exchange
interactions in antiferromagnetic oxides. Varying c value from 0 to 1, one can get a
continuous series of solid solutions, whose magnetic properties change from
antiferromagnetic-like behavior with the Néel temperature TN=523 K for pure NiO to
diamagnetic-like behavior for pure MgO. NicMg1-cO solid solutions were studied in the
present work using optical and EPR spectroscopy methods.
The optical absorption spectra of NicMg1-cO solid solutions can be interpreted using the
energy level diagram of a free nickel Ni2+
ion (3d8) in a cubic crystal field. The observed
absorption bands are as follows: 3A2g (F) →
3T2g (F),
3A2g (F) →
3T1g (F) and
3A2g (F) →
3T1g
(P) (spin-allowed), whereas the remaining ones are spin-forbidden and thus appear as weak
spectra features. With increasing Ni concentration new bands in the spectra appear; the bands
maxima are shifted. These new bands are caused by spin-forbidden electric-dipole transitions: 3A2g(F) →
1Eg(D),
3A2g(F) →
1A1g(G);
1T2g(G),
3A2g(F) →
1T1g(G) and
3A2g(F) →
1Eg(G);
1T2g(G). Their intensity increases rapidly with the nickel content, becoming
comparable to the intensity of spin allowed transitions at c=0.7. Recently, we have
investigated [1] the temperature dependence of the three bands – two electric-dipole 1Eg (D) at
~13500 cm-1
, 1Eg (G) at ~28000 cm
-1 and one magnetic-dipole
3T2g (F) at 8800 cm
-1. All three
bands are sensitive to the magnetic ordering in solid solution; moreover the magnetic-dipole
band involves the Brillouin zone-centre one-magnon contribution, whereas two electric-dipole
bands involve the Brillouin zone-boundary two-magnon contributions [2]. Here we extend our
temperature dependent studies to the case of the 3A2g (F) →
1T1g (G) transition for Ni
concentrations c=0.05, 0.50 and 1.0. The analysis of the absorption spectrum in the range
23000-27000 cm-1
indicates that the 1T1g (G) band width decreases with decreasing
temperature. Comparison of two solid solutions shows that a decrease of the nickel content
results in a decrease of the separation between the 3T1g (P) and
1T1g (G) bands. Such
contradiction could be explained by a variation of the Racah parameter B, which increases
with a decrease of the nickel content due to the change of the Ni–O bonding [1]. The spectra of electron paramagnetic resonance (EPR) were measured at 77 K, 4 K and room
temperature on single-crystal MgO:Ni2+. The angular dependence of the EPR spectra in the (100) and
(110) planes was studied. The overall appearance of the obtained EPR spectra suggests deviation
of the local field from ideal cubic symmetry [3].
Acknowledgment
This work was supported by Latvian Science Council Grant No.402/2012 and Estonian
Science Council No 8699.
[1] N.A. Mironova, U.A. Ulmanis, Radiation Defects and Metal Ions of Iron Group in Oxides
(Zinatne, Riga, 1988).
[2] N. Mironova-Ulmane, V. Skvortsova, A. Kuzmin, I. Sildos, Fiz. Tver. Tela 44, 1403
(2002)
[3] J.W. Orton, J P.Auzins, J.E. Wertz Phys Rev. 119, 1691, 1960
184
PII_25 Magnetic resonance and optical spectroscopy of the tetragonal Yb3+
center
in KZnF3
M.L. Falin1,2)
, K.I. Gerasimov1,2)
, V.A. Latypov1)
, A.M. Leushin2)
,
S. Schweizer3)
, J.-M. Spaeth3)
1)
Kazan Zavoisky Physical-Technical Institute, 420029 Kazan, Russian Federation 2)
Kazan (Volga Region) Federal University, 42008 Kazan, Russian Federation 3)
Physics Department, University of Paderborn, D-33098 Paderborn, Germany
Crystals ABF3 (A = K+, B = Zn
2+) of the perovskite type are promising materials for
applications and appropriate model systems for the corroboration and development of the
theory of electron-nuclear interaction between impurity rare-earth ions and magnetic moments
of ligand ions in the nearest environment (transferred hyperfine interaction). This work
presents the results of the EPR, ENDOR and optical spectroscopy studies of Yb3+
centers in a
KZnF3 single crystal.
KZnF3:Yb3+
single crystals were grown by the Bridgman-Stockbarger method from
the melt consisting of YbF3 or YbF3 and LiF. In contrast to KMgF3 [1], no tetragonal centers
were detected in KZnF3:YbF3, while a new paramagnetic center with tetragonal symmetry
was observed in Li-doped KZnF3:YbF3. The transferred hyperfine interaction of Yb3+
with the
nearest fluorines and Li+ was determined by ENDOR. The analysis of the ENDOR spectra
indicates that Yb3+
replaces Zn2+
(sixfold coordinated position) and that the tetragonal
distortion of the [YbF6]3-
complex is due to the local compensation of the positive excess
charge by a substitutional Li+ at the nearest Zn
2+ site along the C4 direction of the crystal. It
was established that doping of KZnF3 with Yb3+
leads to the tetragonal paramagnetic center
the same as in KMgF3, but with the different local structure. The energy level schemes of the
observed center were determined from the optical spectra and the parameters of the crystal
field potential were calculated.
The crystal field parameters were used to analyze the crystal lattice distortions in the
vicinity of the Yb3+
ion within the superposition model.
The obtained distances were used in the theoretical evaluation of the transferred
hyperfine interaction parameters on the basis of the bonding mechanisms of the rare-earth ion
to ligands developed in [2,3].
This work was supported by the grant NSh-5602-2012.2, the Russian Foundation for
Basic Research (grant 13-02-97031r_Volga region_a) and by the Deutscher Akademischer
Austauschdienst.
[1] M.L. Falin, V.A. Latypov, B.N. Kazakov, A.M. Leushin, H. Bill, D. Lovy
Phys. Rev. B, 61, 9441 (2000)
[2] M.L. Falin, M.V. Eremin, H. Bill, D. Lovy, Appl. Magn. Reson., 9, 329 (1995)
[3] M.L. Falin, O.A. Anikeenok, V.A. Latypov, N.M. Khaidukov, F. Callens, H. Vrielinck,
A. Hoefstaetter, Phys. Rev. B, 80, 174110 (2009)
185
PII_26 EPR of Dy3+
, Er3+
and Yb3+
in Cs2NaBF6 (B = Y, Sc) single crystals
M.L. Falin1,2)
, V.A. Latypov1)
, N.M. Khaidukov3)
1)
Kazan Zavoisky Physical-Technical Institute, 420029 Kazan, Russian Federation 2)
Kazan (Volga Region) Federal University, 42008 Kazan, Russian Federation 3)
Institute of General and Inorganic Chemistry,119991 Moscow, Russian Federation
Fluoroelpasolities having the cubic structure in the wide temperature interval are
perfect model systems in which the isomorphous substitution of cations by trivalent rare-earth
ions provides an opportunity to study optical and magnetic properties of dopants in a wide
concentration range. Unlike widely studied [1-4] chloroelpasolities (A2BLnCl6) doped with
impurity rare-earth ions, fluoroelpasolities (A2BLnF6) are studied much less [5-7]. It is mainly
due to the technical difficulties of their synthesis.This work presents results of the EPR
investigation of Ln3+
ions in Cs2NaYF6 and Cs2NaScF6 single crystals.
Crystals of cubic elpasolites Cs2NaYF6 and Cs2NaScF6 doped with rare-earth ions
were grown under hydrothermal conditions. For hydrothermal experiments, copper-insert
lined autoclaves with a volume of 40 cm3 were utilized, and the inserts were separated by
perforated diaphragms into synthesis and crystallization zones. The fluoride crystals were
synthesized by a direct temperature-gradient method as a result of the reaction of the aqueous
solutions containing 35–40 mol.% CsF and 8–10 mol.% NaF with oxide mixtures (1 − x)Y2O3
− xLn2O3 or (1 − x)Sc2O3 − xYb2O3 at a temperature of ∼ 750 K in the synthesis zone, a
temperature gradient along the reactor body of up to 3 K/cm, and a pressure of ∼ 100 MPa.
Under these conditions, spontaneously nucleated crystals of up to 0.5 cm3 were grown in the
upper crystallization zone of the autoclave for 200 h. The purities of the utilized oxides were
99.99% for rare-earth oxides and 99.9% for Sc2O3.
The parameters of the corresponding spin Hamiltonians, the ground states and their
wave functions were determined. Structural models of the observed complexes were
proposed. The experimental results were analyzed in comparison with those for the same
paramagnetic ions in other hosts.
This work was supported by the grant NSh-5602-2012.2 and the Russian Foundation
for Basic Research (grant 13-02-97031r_Volga region_a).
[1] P. Tanner, Mol. Phys. 58 317 (1986)
[2] F.S. Richardson, M.F. Reid, J. Dallara, R.D. Smith, J. Chem. Phys. 83 3813 (1985)
[3] M.F. Reid , F.S. Richardson, J. Chem. Phys. 83 3831 (1985)
[4] P.A. Tanner, V.V.R.K. Kumar, C.K. Jayasankar, M.F. Reid, J. Alloys Compounds
225 85 (1995)
[5] P.A Tanner, L. Yulong, N.M Edelstein, K.M. Murdoch, N.M Khaidukov,
J. Phys.:Condens. Matter 9 7817 (1997)
[6] P. A. Tanner, L. Ning, V. N. Makhov, N. M. Khaidukov, M. Kirm,
J. Phys. Chem. B 110 12113 (2006)
[7] M.L. Falin, K.I. Gerasimov, V.A. Latypov, A.M. Leushin, N.M. Khaidukov,
Phys. Rev. B, 87, 115145 (2013)
186
PII_27 Multifrequency EPR study of the photoinduced centers in KTaO3 crystal
D.G.Zverev1)
, R.V.Yusupov1)
, A.A.Rodionov1, P.P.Syrnikov
2), and V.A.Trepakov
2,3)
1)
Kazan Federal University, Kremlevskaya 18, Kazan, Russia 2)
Ioffe Physical-Technical Institute RAS, 194021 St-Petersburg, Russia 3)
Institute of Physics AV CR, Na Slovance 2, 18221, Praha 8, Czech Republic
Observation of the UV light-induced optical absorption together with a significant
increase of the dielectric constant in perovskite-type incipient ferroelectrics (SrTiO3, KTaO3,
CaTiO3 etc.) opened the possibility of exploring their properties for optoelectronics. However,
the fundamental physics responsible for the nature of the centers involved in these complex
processes is still not quite clear and needs further elucidation. This study presents an effort to
bring new insight into microscopic structure and properties of the paramagnetic centers
formed in KTaO3 single crystals under UV irradiation.
Electron paramagnetic resonance (EPR) spectra of light-induced centers formed in the
nominally pure KTaO3 under UV-irradiation were observed and studied at T < 10 K in the X-
band (9.6 GHz) and Q-band (34 GHz). In the Q-band the signals with the characteristic for
tetragonal centres angular dependences were found that differed significantly from the
dependences observed earlier in the X-band [1]. Studies of these spectra isochronous
annealing have shown that the signals observed in the Q and X-bands are of the identical
origin. EPR line positions with respect to the orientation of the magnetic field for these
centres in either the X or Q-band can be described within the frames of a simple model of
axial centre with S=1/2 and anisotropic g-factor. However, while in the X-band g < g||, the
situation in the Q-band is opposite, g < g||. Moreover, in the Q-band no trace of the spectra
observed in the X-band was found and vice versa. The correspondence between the EPR
spectra parameters for the two bands is presented in the Table.
Center X-band [1,2] Q-band
g|| g g|| g
I 2.08 1.17 ~2 2.50
II 2.09 1.35 ~2 2.76
III 2.04 1.73 ~2 2.17
The described experimental results indicate clearly that the spectra observed in the X
and Q microwave bands correspond to the different transitions within the ground state of the
photoinduced species. This conclusion is not compatible with the models proposed in [1, 2],
the situation is turned out to be obviously more complicated. The possible model of these
centers is the exciton in the triplet state formed by the electron at the tantalum and hole at the
oxygen. Another degree of freedom that complicates the situation is the strong spin-orbit
coupling of the heavy Ta ion.
[1] Laguta, V.V., et al. Phys. Rev. B, 1995. 52(10): p. 7102-7107.
[2] Maiwald, M. and O.F. Schirmer. Europhys. Lett., 2003. 64(6): p. 776-782.
187
PII_28 Multipole interactions between Tm3+
ions in LiTmF4
I.V. Romanova, B.Z. Malkin, M.S. Tagirov
Kazan Federal University, Kazan, 420008, Kremlevskaya 18, Russian Federation
Double lithium-rare earth fluorides which crystallize in the tetragonal scheelite
structure are considered for many years as model objects in physics of dipolar magnets [1].
The unit cell of LiTmF4 contains two magnetically equivalent Tm3+
ions at sites with the S4
point symmetry. The ground state of Tm3+
ions in the tetragonal crystal field is the singlet 2,
and the nearest excited crystal field sublevels of the ground 3H6 multiplet are the 34 doublet
and the 1 singlet with energies of 30 and 60 cm-1
, respectively. Studies of spectral, magnetic
and magnetoelastic properties of LiTmF4 revealed strong interactions of Tm3+
ions with
lattice strains [2-4]. In particular, LiTmF4 exhibits a giant forced magnetostriction at liquid
helium temperatures [2].
To interpret temperature and magnetic field dependences, as well as dependences on
the magnetic field orientation in the basis a-b plane, of the magnetic susceptibility,
magnetization and parastriction, in variance with the earlier theoretical analysis [2-4],
multipole interactions between the Tm3+
ions are taken into account in the present work.
Parameters of the multipole interactions were calculated by making use of the characteristics
of the lattice dynamics of the LiTmF4 crystal lattice and the electron-phonon coupling
constants determined earlier [2].
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0
30
60
90
120
150
180
210
240
270
300
330
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Ma
gn
etiza
tio
n (
Bo
hr
ma
gn
eto
n p
er
ion
) 1
2
3
4
5
Fig. 1. Calculated (solid curves) angular
dependences of the magnetization of LiTmF4
single crystal as compared with the results of
measurements (symbols) at T=4.2 K in the
external magnetic fields B= 0.3 (1), 1 (2), 2
(3), 3 (4) and 5.5 (5) T.
The simulated temperature, magnetic field and angular dependences of the magnetization,
field and angular dependences of first exited energy level are in good agreement with the
experimental results [3,4]. It follows from calculations that magnetoelastic interactions and
electron-phonon interactions in double lithium-rare earth fluorides contribute essentially to
the magnetization in external magnetic fields at liquid helium temperatures.
This work was partially supported by RFBR grant 12-02-00372-a.
[1] L.K. Aminov et al., Handbook on the Physics and Chemistry of Rare Earths, v. 22, North
Holland, Amsterdam, (1996).
[2] V.I. Krotov et al., Sol. St. Phys. 24, 542 (1982).
[3] D. I. Abubakirov et al., J. Phys.: Conference Series 51, 135 (2006)
[4] R.Y. Abdulsabirov et al., J. Lumin. 117, 225 (2006), R.Y. Abdulsabirov et al., SPIE Proc.
4766, 59 (2002).
188
PII_29 Trivalent ions of zirconium and hafnium in yttria ceramics
V.I. Solomonov, A.V. Spirina
Institute of Electrophysics of the Ural Branch of the Russian Academy of Science,
620016, 106, Amundsen str., Ekaterinburg, Russia
E-mail: [email protected]
Neodymium and ytterbium doped yttria ceramics are used as gain mediums for solid
lasers [1]. The oxides of zirconium or hafnium were introduced as sintering additives to
improve the ceramics quality due to increasing its density and transparency [2]. Also, these
additives are used to obtain a disordered crystal field into ceramics in order to widen gain
bands of neodymium or ytterbium ions [3]. Zr4+
and Hf4+
ions with closed electronic shells
cannot be acceptors or donors for exited Nd3+
or Yb3+
ions. However the Zr3+
and Hf3+
ions
can execute so role. These ions possess similar ground state electron configurations of [Kr]4d1
(Zr3+
) and [Xe]5d1 (Hf
3+). In the crystals these electron configurations form an orbital doublet
(E) and triplet (T2). At the same time, no information on presence of the Zr3+
and Hf3+
ions in
yttria ceramics are present in literature.
We investigated pulsed cathodoluminescence (PCL) and electron paramagnetic
resonance (EPR) of yttria ceramic doped up to 10 mol% HfO2 (ZrO2) with the purpose of
detection of Zr3+
and Hf3+
ions. We found out a new band at 818 nm in PCL spectrum. It
is in agreement which optical transition from orbital triplet T2 to double E of Hf3+
and Zr3+
.
Also we discovered a paramagnetic signal in EPR spectrum. The EPR signals
observed in the region of B = 2400–3700 Gs for the samples of ceramics containing zirconia
and hafnia should be assigned to the presence of paramagnetic trivalent Zr3+
and Hf3+
ions. In
the same crystal fields, Zr3+
and Hf3+
ions exhibit almost identical structures of energy levels
and approximately the same Zeeman splitting in external magnetic field. Both ions exhibit a
hyperfine structure in the EPR spectrum, which is indicative of the interaction between the
spin of unpaired electron and magnetic field of the nucleus. The parameters of EPR signals
are presented in the table 1.
Table 1. The parameters of EPR signals
Ion g-factor broadband, H, G Intencity
Hf3+
2.83856 45.1 1.83
1.9909 32.0 3
1.98886 118 6
1.97219 21 6
Zr3+
4.2066 63.33 0.27
3.86555 55.5 0.46
2.8345 41.6 0.7
1.9979 35 2
1.9916 98 2.2
1.9713 15 1.5
The work was supported by the Programs of the Presidium of the Ural Branch of RAS
and RFBI (11-08-005a)
[1] Ikesue A., Kamata K., Yoshida K. J. Am. Ceram. Soc., 79, 359 (1997).
[2] Hou X., Zhou S., Li Y., Li W. Opt. Mater., 32, 920 (2010).
[3] Osipov V.V., Solomonov V.I., Shitov V.A., et al. Optika atmosphery i oceana, 25, 207
(2012)
189
PII_30 Thermodynamics of Ising rare earth magnet in the static fluctuation approximation
A.A. Khamzin, R.R. Nigmatullin
Kazan (Volga Region) Federal University, 420008, Kremlevskaya str. 18, Kazan, Russia
Magnets with large single-ion anisotropy comparable to the exchange interaction
evoke considerable interest, in particular, the cases, where such anisotropy is becoming
comparable with exchange interaction. The single-ion anisotropy differs in its influence from
many-ion anisotropies of exchange or dipole nature [1], which are usually considered in the
quasi-classical approach. The single-ion anisotropy plays a significant role not only in spin
dynamics (see review [2] and references therein) but also in phase transitions in formation of
magnetically ordered states, especially in cases when these transitions are induced by a
magnetic field. As a result of the interplay between the single-ion anisotropy of the easy-plane
type and isotropic exchange interaction, which can take place, for instance, in easy-axis
magnets with spin S=1 at a site, the transition to a magnetically ordered state occurs as a
quantum phase transition of the displaced type mediated by spontaneous formation of spin
(magnetic) polarization of Van-Vleck single-ion states oriented in the easy plane [3].
In the given paper the authors (in the frame of the original the static fluctuation
approach (SFA)) obtained the closed self-consistent system of equations for calculation of the
desired thermodynamic values of the Ising magnet with arbitrary spin and one-ion anisotropy.
The essence of the SFA is based on accurate calculations of fluctuations of molecular field
[4]. As an example the complete analysis of the critical behavior of the Ising magnet with spin
S=1 (Blume-Capel model [5]) was realized. This model has a specific peculiarity. If the
constant of easy-plane/one-ion anisotropy accepts sufficient value and starts to compete with
the constant of exchange interaction then phase transition from the paramagnet state to the
ordered state should be considered as the phase transition of the first order. This peculiarity is
evoked by the one-ion anisotropy constant of the easy-pale type which makes the
nonmagnetic state of the singlet as the ground state [6]. The expressions for the phase
transitions lines of the first and the second order were found. In addition, the coordinates of
the tricritical point for some types of cubic lattices were found also. These analytical results
are in accordance with numeric results obtained by the Monte-Carlo method [7].
References
[1] A. F. Andreev and V. I. Marchenko, Sov. Phys. Usp. 23 (1), 21 (1980).
[2] V. M. Loktev and V. S. Ostrovskii, Low Temp. Phys. 20 (10), 775 (1994).
[3] V. M. Kalita and V. M. Loktev, JETP 98 (5), 1006 (2004).
[4] R. R. Nigmatullin, A. A. Khamzin, H. B. Ghassin, Phys. Rev. E 61 (4), 3441 (2000).
[5] M. Blume, V. J. Emery and R. B. Griffiths, Phys. Rev. A 4, 1071 (1971).
[6] A. K. Zvezdin, V. M. Matveev, A. A. Mukhin, and A. I. Popov, Rare-Earth Ions in
Magnetically Ordered Crystals (Nauka, Moscow, 1985) [in Russian].
[7] M. Deserno, Phys. Rev. E. 56, 5204 (1997).
190
PII_31 Shift of the atomic spectra in the rotatory reference frame
T.A.Kudykina, A.I. Pervak
“Ukraina” University, 1-G Horiva Street, Kyiv 04071, Ukraine
E-mail: [email protected]
It is shown that in the non-inertial reference frame, the atomic spectra have red shift
(or blue shift). From the law of energy conservation, the difference of the frequencies in two
reference frames (the rotatory and motionless) is equal : /qH h ,where 0/qH hL
is the angular momentum, 0 is a wavelength of emitted light in a motionless reference
frame, L is a perimeter of the emitting object,
is the angular velocity of the emitter.
On the other hand, the difference of the frequencies, obtained from the Sagnac effect, is
0 /c Rn c , n
is the normal to the emitting surface. If the angle between n
and
is
more than /2, the cosine of this angle is negative, and the blue shift of the spectrum will be
observed. Denote, /Rn c . Here R is a radius of the emitter, 0 is a frequency of
emitting light in a motionless reference frame. The spectrum shift z is defined in
wavelength as 1 0 0( ) /z , where 1 is the wavelength of the observed emission from a
cosmological object. The relation between z and is: /(1 )z . It is seen that the
parameter z does not depend on the wavelength 0 (as it has been observed formerly). But it
does however depend on the light frequency 0 . The research conducted shows that the main
reason of the redshift (or blue shift) of the spectrum of emitted light is the rotation of stars,
quasars and galaxies, their non-inertial reference frame. The parameter of the spectrum
redshift z of the cosmological object depends on its radius and angular velocity.
The parameter z does not determine the distance from us to the cosmological object
and time dilation of the expanding Universe .
The distribution function of value z for the visible light, in a model of black-body
emission, has been obtained:
)1)1
(exp()1(
),(4
z
bz
zAbzf . Here
kTb 0 . Its
comparison with the observed distribution function shows, that the temperature of emitting
surfaces of the cosmological objects is in the range of KT 310)1.63( .
Now, the estimation of the irradiated energy of quasars will not exceed on several
orders the irradiated energy of the hot stars. The age of the Universe and the ages of quasars
and galaxies, as such, better correlate with each other.
191
PII_32 Influence of conduction band energy on the level structure
of transition metal ions
N.R. Rudoman, Е.N. Tumayev
Kuban State University, 350040, Stravropolskaya str., 149, Krasnodar, Russia
E-mail: [email protected]
One of the quantum electronics materials are wide band gap semiconductors doped
with transition metal ions [1]. In the study of the spectral properties of the ions in these
environments should consider the effect of the conduction band, which appears in the
scattering of electrons delocalized electrons localized on the optical center. We have analyzed
the effect of the conduction band at the position of the energy levels of the impurity 3d1-ion.
The Hamiltonian describing the system under consideration, in which the interaction between
the electron and the optical center of a delocalized electron is regarded as a perturbation of the
form
211021 ,, rrKrHrrH (1)
where 1r is the radius vector of the electron in the optical localized impurity center, 2r –
radius vector of the delocalized conduction band electron, 10 rH
– Hamiltonian of the
electron optical center, which takes into account the interaction with the atomic core and a
ligands field. The first term in (1) is the kinetic energy of the trapped electron, the second –
the potential energy of interaction of the electron with the atomic core, and the third describes
the interaction of an electron impurity center with ligands. The electrostatic interaction of the
localized electron and the electron conduction band is taken into account term
2
1 2 1 2, /K r r e r r .
Two-electron wave function 1 2,r r
of the Hamiltonian (1) is constructed as a
symmetric or ant symmetric combination of the products of the localized wave function that is
selected in the Rydberg form 1 1 1,nl lmnlm R r Y
comprising a radial portion 1nlR r
and a spherical function 1 1,lmY
, and the delocalized electron wave function of the
conduction band. For the initial state wave function is chosen by us as a plane wave
2 2 2expk ik r where 2k
the wave vector of the incident wave. The wave function of the
final state is chosen as a diverging spherical wave 2 2 2 2exp /k f ik r r
where f
is
the scattering amplitude and 2k is the wave vector of the scattered wave, and for the elastic
scattering 2 2k k .
Selected wave functions of the initial and final states allowed us to estimate the matrix
elements nlm K nlm
in the approximation when the amplitude of the scattering is
independent of the scattering angle, which is quite well for low-energy electrons, and get
corrections to the energy levels of the impurity ion.
[1] K.A. Kikoin, V.N. Fleurov. Transition Metal Ions in Semiconductors: Electronic Structure
and Physical Properties. World Scientific Publishing Co., Singapore, 1994, 354 p.
192
PII_33 Evaluation of absorption spectrum of trivalent chromium doped
lithium niobate crystal
К.S. Avadov, М.V. Sukachev, Е.N. Tumayev
Kuban State University, 350040, Stravropolskaya str., 149, Krasnodar, Russia
In this work the results of calculating the location of the energy levels of the Cr3+
ion for
lithium position in the crystal lattice of LiNbO3 are given. With this purpose the formulas of
crystal field theory have been adapted for the case of trigonal symmetry C3v. Consideration of
Coulomb interaction allowed to express the matrix elements of the Hamiltonian for the
electron optical system of impurity ion by three semi-empirical parameters: the effective
charge of the impurity ion Zion, and the parameters of Racah B and C, with the help of which
the energy levels of Cr3+
[1] ion were calculated.
The results of numerical calculation that used the fitting of theoretical values of energy to
the experimental data by method of least squares, allowed to determine the following values
of the above parameters: Zion=5.36, B=341 cm–1
, C=3238 cm–1
. Below we consider energy
levels obtained theoretically at the data Zion, B and C.
The ground state from which the electronic transitions occur in the absorption is 4A2 (A1,
A2, E - the irreducible representations of the point group C3v), the energy of which is assumed
to be equal to zero. In the absorption spectrum of lithium niobate with chromium there
observed a series of the narrow lines (R-lines) corresponding to transitions from the ground
level to the 2E. The theoretical calculation shows that
2E energy is equal to 12099 cm
-1. The
doublet with energies 13820 cm-1
for components E1/2 and 13782 cm-1
for the component E3/2
is observed in the experiment.
Similarly, the transitions from the ground state to the terms 2A1 and
2A2 accord to narrow
bands in the absorption spectrum. The calculation shows that the energy 2A1 is equal to 22698
cm-1
, and 2A2 is 12143 cm
-1. Presumably, the experimentally observed band of 20200 cm
-1
corresponds to transition 4A2→
2A1, and band 14630 cm
-1 – corresponds to transition
4A2→
2A2.
In accordance with the experiment, the terms (e2e')
4E and
4A1 (in brackets the genealogy
of the term is specified, i.e. a three-electron configurations generating the given term, the
symbols e and e' denote the E-representation for single-electron configuration, the character
stroke mark the fact that this representation corresponds to two doubly degenerated levels
with different energy values and a different set of wave functions) have energies 15330 cm-1
and 15300 cm-1
respectively. According to performed calculation, 16414 cm-1
is the energy of
(e2e')
4E, 16383 cm
-1 is the energy of
4A1. The wide band in the absorption spectrum,
traditionally referred to as the U-band, is explained by the transitions to these levels from the
ground state. In the approximation of cubic symmetry (point group symmetry O) the levels
(e2e')
4E and
4A1 corresponds to the level of triply degenerated
4T2 level with multiplicity equal
to 4.
The further analysis of the experimental data shows the presence of a wide Y-band in
absorption. It is considered that this band is caused by the transitions from level 4A2 to levels
(a1ee')4A2 with the energy of 21390 cm
-1, and (a1ee')
4E with an energy of 20850 cm
-1. The
developed theory gives to (a1ee')4A2 energy the value of 20960 cm
-1 and 19353 cm
-1 for
(a1ee')4E energy. These two levels correspond to the term
4T1 in the case of cubic symmetry
group.
[1] К.S. Avadov, Е.N. Tumayev. The spectroscopic properties of chromium ions in lithium
niobate crystal, Optics and Spectroscopy (In Russian), 2010, V. 109, # 3, p. 379-384.
193
PII_34 Kinetics of up-conversion of electronic excitations in active media
of solid-state lasers
I.V. Kochubey, М.V. Sukachev, Е.N. Tumayev
Kuban State University, 350040, Stravropolskaya str., 149, Krasnodar, Russia
E-mail: [email protected]
One of the co-operative processes that takes place in active media with high levels of
excitation is the up-conversion of electronic excitation [1-3], in which the interaction of two
similar excited centers (donors) result to summarizing of their excitation in accordance with
the following scheme **** DDDDDD .
The microscopic equations that describe the up-conversion in accordance with the
instructions above have the following form:
trntrnA
dt
trntrndDDD
DD ,,2,,
2121
r
DDDDDD rptrnrrrrWtrntrn ,1,,, 2121 , (1)
where trnD , – are the local densities of the excited donors, rpD – the projection operator
on the sites occupied by impurity centers (donors), 6
2
6
1
21 ,rrrr
CrrrrW DD
DD
–
probability of electronic excitation energy transfer from the excited donor sites 1r , 2r to the
un-excited donor in site r in time unit, DDC – micro parameter of donor-donor interaction,
DA – the rate of the spontaneous decay of donor excitation (both radiation and non-radiation).
Averaging of the equation (1) in assumption of random spatial distribution of impurity
centers allows finding the spatial correlation function for the donor excitations
trntrn DD ,, 21 , from which the following expression is obtained for the average
concentration of excited donors equal to ttAntn DDD exp0 , where loss function
t is given by various analytical expressions for three different time stages. In the first
stage, when the up-conversion processes occur in closely spaced pairs of excited impurity
centers, t is proportional to 4/1t . In the second stage the up-conversion processes occur
between spaced relatively far excited donors, while the dumping kinetics of the donor
excitation have Foerster’s character, t is proportional to 2/1t . On the third and final stage
there is no up-conversion, and the kinetics is of exponential character.
[1] Kii-Soo Lim, P. Babu, Sun-Kyun Lee et al. Infrared to visible up-conversion in thulium
and holmium doped lutetium aluminum garnet. J. Lumin. 2003, Vol. 102-103, p.737-743.
[2] Xiaodong Xu, Zhiwei Zhao, Pingxon Song et al. Upconversion luminescence in Yb3+
-
doped yttrium aluminum garnets. Physica B, 2005, Vol. 357, p. 365-369.
[3] J.C. Vial, R. Buisson, F. Madeore, M. Poirier. Up-conversion studied by selective time
resolved excitation techniques in Pr3+
: LaF3. J. de Physique, 1979, T. 40, No.9, p.913-920.
194
PII_35 Changes in optical properties of UV irradiated Ce-doped KY3F10
and double-doped KY3F10:Ce3+
,Yb3+
crystals versus temperature
E.Yu. Tselischeva, A.K. Naumov, D.I. Tselischev, S.L. Korableva
Kazan Volga Federal University, Kazan, Russia
Now it is known that in the most fluoride crystals doped by Ce3+
ions color centers
(CC) formation after UV irradiation occurs. This process often is interfering factor for
achieving gain in crystals that might be used as active media. In previous works [1,2] it has
been shown that Yb3+
ions in Ce-activated crystals effectively suppress CC formation process.
In this work we present the results of investigation of temperature behavior of optical
properties of KY3F10:Ce3+
and KY3F10:Ce3+
,Yb3+
crystals after UV irradiation by 4ω0 of
YAG:Nd. Appearance of additional absorption bands in all samples after UV irradiation was
observed. In crystal KY3F10:Ce3+
these bands are changed over time. These bands are
corresponded with absorption of CC. In case of additionally doped by Yb3+
ions K3YF10:Ce3+
crystal these changeable bands weren’t observe after UV irradiation. As a result it was
concluded those Yb3+
ions in KY3F10:Ce3+
crystal contribute to processes of bleaching of CC,
which are formed after UV exposure.
To explain this fact it was necessary to estimate positions of the ground states of CCs
the ground states of Ce and Yb ions relatively the valence and the conduction bands of crystal
KY3F10. For this purpose optical spectra of the crystals KY3F10:Ce, KY3F10:Ce,Yb were
continuously measured in temperature range 300 – 750 K. The absorption bands that appeared
after UV exposure disappeared in turn when the temperature rises. It was revealed that in
crystal KY3F10:Ce at least two types of CC are presented. Activation energy of these CC were
estimated. Positions of the ground states of Yb ions in bivalent state were defined. Using
these data positions of the ground states of other rare earth (RE) ions in bivalent and trivalent
state were calculated.
The diagram of energy levels for RE ions and CCs and transition of charge carriers
between their levels were constructed in crystal KY3F10 as the results of this study.
[1] E.Yu. Tselischeva et al. “Optical Properties of UV Induced Color Centers in a
KY3F10:Ce3+
Crystal”, Optics and Spectroscopy, Vol. 114, No. 6, pp. 822–826 (2013)
[2] E.Yu. Koryakina et al. “Spectroscopic properties of color centers in crystal KY3F10:
Ce3+
co-doped by Yb3+
ions” in Proc. XIV Feofilov Symposium, P.We-P-57 (2010)
195
PII_36 Energy levels of Tm3+
ions in YF3 crystal
V.V. Pavlov, B.N. Kazakov, S.L. Korableva
Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russian Federation
Energy-level diagram of Tm3+
ions was constructed by means of luminescence upconversion
investigation in YF3:Yb3+
/Tm3+
system [1] under λ=980 nm excitation.
YF3:Tm3+
(0.5%) system was studied at 300K and 77K. Luminescence of Tm3+
ions was
excited by two methods: UV radiation in 42000 – 40000 cm-1
region and resonance at 3P2,
3P1
and 3P0 levels. Both Tm
3+ ions excitation methods result in similar luminescence spectra in
200-1000 nm range (Fig. 1).
Energy-level diagram of Tm3+
ions was constructed and Stark structure of 3H6 ground-state of
Tm3+
ions in YF3:Tm3+
(0.5%) crystal was determined.
200 300 400 500 600 700 800 900 1000
0
5000
10000
15000
20000
600 650 700 750 800 850 900
In
tens
ity
(a.u
.)
Wavelength (nm)
Inte
nsi
ty (
a.u.)
Wavelength (nm)
Fig. 1. Luminescence spectrum of YF3:Tm3+ (0.5%) 77K under 250 nm excitation. Inset:
magnification of the spectrum in 600 – 900 nm spectral range
References:
[1] W. Guofeng, Q. Weiping,W. Lili, W. Guodong, ZH. Peifen, ZH. Daisheng, D. Fuheng,
Journal of rare earths, 27, 330 (2009)
196
PII_37 Photoinduced charged lattice of ruby
D. A. Bizyaev, A. A. Bukharaev, Yu. V. Vladimirtsev, K. I. Gerasimov, N. K. Solovarov
Zavoisky Physical–Technical Institute, Kazan Scientific Center, Russian Academy of
Sciences, 420029, Sibirsky tract 10/7, Kazan, Russia
The intense optical irradiation (λ ≥ 400 nm) at low temperature (T <150 K) creates in the
concentrated ruby the photo-induced electrical "domain" structure that conserved at room
temperature [1-3]. These "domains" formed in the irradiated part of the sample have the same
in magnitude and opposite in direction the internal permanent electric fields that are directed
parallel to an optical axis. Electric fields are presumably formed as a result of spatial orderly
redistribution of photo-induced abnormally charged ions of chromium (Cr2+
, Cr4+
) due to the
absolute negative photoconductivity [2]. Estimates of the size and shape of "domains" from
experiments on photon echo in the sample of ruby with previously formed "domain" structure
show that the “domains” have the form of plane-parallel plates of up to 0.4 mm in length and
a thickness of ≈ 20 μm oriented perpendicular to an optical axis [4 ].
We report the observation by the use of an atomic force microscope (AFM) the fixed charge
lattice with a period ≈ 1 μm, recorded on the surface of concentrated ruby after low-
temperature (77 K) irradiation with an argon laser (λ = 514.5 nm) (left figure). In the ruby
plate (thickness of 0.4 mm, the concentration of 0.4 wt. % Cr2O3) cut nearly perpendicular to
the optical axis (angled 5.8 º) created domain structure, which is manifested in the splitting of
R1-line of luminescence (as in [1-3]). Charged planes perpendicular to the optical axis of ruby
(left figure) form a structure of a plurality of microscopic planar capacitors with internal
uniform electric fields directed parallel to the optical axis. The distance between the charged
planes is ≈ 17 nm. They hypothetically formed out of abnormally charged ions: Cr2+
- the
negative planes, Cr4+
- the positive ones. The right figure shows the distribution of potential
(Kelvin mode) on the surface of ruby after the creation of the charge lattice due to the effect
of the alternating voltage on the needle of AFM +5 V (light stripes) and -5 V (dark stripes).
[1] P. F. Liao, A. M. Glass, L. M. Humphrey. Phys. Rev. B 22, 2276 (1980).
[2] S. A. Basun, A. A. Kaplanskiĭ, and S. P. Feofilov. Sov.Phys. JETP. 60, 1182 (1984).
[3] N. N. Kurkin, Yu. E. Nesmelov, N. K. Solovarov. Phys. Sol. State. 39, 295 (1996).
[4] S. P. Feofilov, Ki-Wan Jang, R. S. Meltzer. Phys.Rev. B50, 13138 (1994).
197
PII_38 CoO luminescence excited by synchrotron radiation
V.I. Sokolov1)
, V.A. Pustovarov2)
, V.N. Churmanov2)
, N.B. Gruzdev1)
, P.S. Sokolov3)
,
A.N. Baranov3)
1)Institute of Metal Physics UB RAS, 620990, S. Kovalevskaya str. 18, Ekaterinburg, Russia
2)Ural Federal University, 620002, Mira str. 19, Ekaterinburg, Russia
3)Lomonosov Moscow State University, 119991, Moscow, Russia
Investigation of energy spectrum of oxides of 3d-transition metal is the actual problem of the
condensed matter physics. Experimental researches of interband transitions of NiO and CoO
oxides are realized by the methods of optical spectroscopy and inelastic X-ray scattering.
Recently the interesting results were achieved in connection with the observation of
photoluminescence (PL) and photoluminescence excitation (PLE) spectra of NiO using
synchrotron radiation (DESY, Hamburg) [1]. High intensity of synchrotron radiation
improves significantly the possibilities of PL observation and allows us to register the PLE
spectrum in wide energy interval. In this paper the using of synchrotron radiation allowed us
to observe photoluminescence of CoO for the first time. The samples of CoO were the tablets
which has been pressed from the Sigma Aldrich powder.
Fig. 1
Time resolved CoO luminescence.
(1) PL (fast window) (T=8 K; Eexc=6.2 eV)
and PLE spectrum in fast window (2)
and time integrated window (3)
(T=8 K; Elum=3 eV).
In Fig.1 the PL and the PLE spectra are
presented at the impulse excitation at the
length of the impulse of 1 ns. The decay of
photoluminescence was observed in time
interval of 1-80 ns. The PL spectra and
PLE spectra were registered in two temporary windows of (1-5) and (50-60) ns after the
excitation impulse and also the time integrated registration 1 – 80 ns. The PL spectrum
presents the wide band in the interval of 2.5 – 3. 5 eV, whose intensity was changing in
dependence on excitation energy. The PLE spectra differ significantly for the fast, slow and
time integrated registration. In the region of 3 – 7 eV the excitation in the fast window
prevails, in the region of 8 – 11 eV the excitation in the slow window is the most intensive.
As soon as no experimental PLE spectra in the region of interband transitions for CoO are
described in the literature, the preliminary results are interpreted in comparison with the PL
and PLE spectra in NiO [1].
The work was partially supported by the Ural Branch of RAS (grant 12-u-2-1030).
[1] V.I. Sokolov, V.A. Pustovarov, V.N. Churmanov, V.Yu. Ivanov, N.B. Gruzdev, P.S.
Sokolov, A.N. Baranov, A.S. Moskvin, Phys. Rev. B, 86, 115128 (2012)
2 3 4 5 6 7 8 9 10 110,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1,0
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1,0
Inte
nsit
y,
arb
.un
its
Photon energy , eV
1
2
3
198
PII_39 Fluctuations of orbital order in KCuF3 related to antiphase local rotations
V. V. Iglamov, M. V. Eremin
Institut of physics, Kazan (Volga region) federal university, 420008, 18 Kremlevskaya St.,
Kazan, Russian Federation
Recently the new type phase transition was observed in KCuF3 by EPR, optical and Raman
spectroscopy [1-3]. At lowering temperature (T<50 K) the orbital order along c-axis showed zig-
zag or local antiphase rotations of CuF6 fragments. We have analyzed the interaction of Cu orbital
states via elastic field as a possible reason this interesting phenomenon. Using the general
expression of the interaction via elastic field, related to local rotations [2], we have calculated the
values of such interaction parameters for different pairs of Cu-orbital states and found that they
are relatively small. However the qualitative picture of local rotations well corresponds to
experimentally observed pattern. Next interesting result we found is that the interaction via
elastic field yields more stable orbital order in a-b plane with compare to orbital order along c-
axis. Therefore we expect that the melting of orbital order at first starts along c-axis and only then
in a-b plane. This phenomenon is not observed in KCuF3 yet. However, recently such interesting
behavior of orbital melting was observed in LaMnO3 by NMR at oxygen sites.
[1] M.V. Eremin, D.V. Zakharov, H.-A. Krug von Nidda, R. M. Eremina, A. Shuvaev, A.
Pimenov, P. Ghigna, J. Deisenhofer, and A. Loidl, Phys. Rev. Lett. 101, 147601 (2008)
[2] Deisenhofer, J. et al. Optical evidence for symmetry changes above the Néel transition of
KCuF3. Phys. Rev. Lett. 101, 157406 (2008)
[3] James C. T. Lee, Shi Yuan, T.& Siddhartha Lal,Young I Joe, Yu Gan, Serban Smadici, Ken
Finkelstein, Yejun Feng, Andrivo Rusydi, Paul M. Goldbart, S. Lance Cooper and Peter
Abbamonte, Nature Phys. 8 , 63 (2012)
199
PII_40 Multi-frequency (9 and 94 GHz) ELDOR/ ENDOR investigations
of hyperfine interactions
V. O. Erofeev, M. R. Gafurov, G. V. Mamin, S. B. Orlinskii
Institute of Physics, Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russia
Pulsed electron paramagnetic resonance (EPR) methods for determination of small
hyperfine (HF) interactions in multinuclear systems are presented. The advantages and
disadvantages of double resonance techniques such as electron-electron (ELDOR) [1] and
electron-nuclear (ENDOR) [2] methods are demonstrated by the example of detection of HF
interactions in γ-irradiated LiF.
Fig.1 presents pulsed EPR detected ELDOR and ENDOR spectra at 9.7 GHz and 94
GHz at T = 297 K collected on Bruker ELEXSYS 580/680 spectrometer. Positions of the
holes caused by the excitation of forbidden transitions correspond to the frequencies of
nuclear transitions of the spin system for ELDOR. The entire hole pattern is obtained by the
recording the integrated intensity of the FID while varying the frequency difference.
The ENDOR method requires a special resonator, a synthesizer and a radio frequency
amplifier. The ELDOR method requires a second synthesizer and a microwave amplifier. No
special resonator is required for ELDOR measurements.
The advantages of applying of high frequencies are evident (Fig. 1). However, the
intensities and the widths of the lines in ELDOR and ENDOR spectra differ each from other.
We can conclude that the complementary use of both methods at different frequencies is
desirable for the elucidation of the nature of paramagnetic centers.
20 40 60 50 100 150 200 250
L(
19F)
L(
7Li)
W-band
(3.3 T)
ELDOR detected NMR
ENDOR
X-band
(0.34 T)
L(
7Li)
ENDOR
ELDOR detected NMR
NMR frequency (MHz)
L(
19F)
Fig. 1. Pulsed EPR detected ELDOR and ENDOR spectrum of γ-irradiated LiF at 9.7 GHz (left panel) and 94
GHz (right panel) at T = 297 K .
[1] P. Schosseler, Th. Wacker, A. Schweiger, Chem. Phys. Lett., 1994, 224: 319
[2] D. M. Murphy and R. D. Farley, Chem. Soc. Rev., 2006, 35: 249
200
PII_41 Centres of luminescence in LiF-U crystals
M.M. Kidibaev, G.S. Denisov
Kyrgyz Academy of Sciences, Institute of Physical-Technical Problems and Material
Engineering
It is assumed that introducing of heterovalent uranium admixture in LiF crystal may cause
formation of several types of centers which differ by ways of compensation of the redundant
positive charge inserted by U6+
ions. For instance, Ranciman [1] has offered the model of a
center that contains the U6+
ion at the lithium site surrounded by oxygen ions O2–
substituting
for all six adjacent fluorine ions. Redundant negative charge of such center is locally
compensated by anionic vacancy (vа) in the second coordination sphere. Such model is
implicating an evidence of the preferential direction oriented along the symmetry axis of third
order.
It was reliably found by Feofilov [2] when investigating polarization properties of
luminescence that the luminescence center is oriented along C4 axis, and he offered
alternative model of the center where oxygen ions substitute not for all six fluorine ions
surrounding U6+
ion, but only for five of them. We observe the F-band in optical absorption
spectra of LiF(U) crystal. This fact indicates on possible localization of redundant electron
from one of the six oxygen ions at the anion vacancy forming the F-center, and allows to
“reconcile” Ranciman model with the results of polarization studies by Feofilov. Really, an
anisotropy of the center of luminescence containing not positively charged vacancy but
electroneutral (relative to the lattice) F-center will be defined by asymmetry in the charge
distribution in the bunch (O2–
– U6+
– O–) oriented along C4 axis. Structural formula of the
center can be written as [U6+
5Oa2-
Oa- (va
+ e
-)].
When anion admixture (ОН- или SO4
2-) is added as a co-activator, the F- centers do not
appear.
[1] Runciman W.A. Nature. 1955. V. 175, 645.
[2] Feofilov P.P. Optics and Spectroscopy, 1959. v. 7. N 6, 842.
201
PII_42 Polaron in biatomic linear chain: perturbation theory approach
A.L. Larionov
Kazan Federal University, 420008, Kremlevskaya Str. 18, Kazan, Russian Federation
Linear biatomic chain with interaction between excitation and vibration degrees of
freedom is used as the simple model for research polaron-like states. The unperturbed systems
are: long wave optical longitudinal vibrations of biatomic chain with frequency ω (or
vibrations of a sublattice of atoms with masses m) and nonexcited atoms. The perturbations in
notation [1] are: transfer of excitations from vibrating atoms n on nearest neighbour atoms
n+1, n-1 of another sublattice:
-J (φn φ*n+1 + φn φ*n-1);
interaction between vibrations and excitations, which is proportional to displacement x and to
excite occupation number of atom with mass m:
-χ φn φ*n x ,
and asymmetrical anharmonicity. To receive harmonic as well as anharmonic potentials of
third V3(x) and fourth V4(x) orders with minimum number of parameters, we used on-site
Morse potential:
V(x)=D[exp(-αx)-1]2.
In that case 2Dα2=mω
2 and V3(x) = - Dα
3x
3 and V4(x) = 3.5 Dα
4x
4.
Wave functions of zero-order basis consist of eight triple products |kn-1> |kn> |kn+1>
(k=0,1). Energy spectrum of mixed excitation-vibration states is found in second order
perturbation theory.
[1]. M.A. Fuentes, P. Maniadis, G. Кalosakas, K.O Rasmussen, A.R. Bishop, V.M. Kenkre,
Yu.B. Gaididei. Phys. Rev. E 70, 025601(R) (2004).
202
PII_43 EPR studies of the mechanochemically doped fluorites
I. A. Irisova, A. A. Rodionov, D. A. Tayurskii, and R. V. Yusupov
Kazan Federal University, 420008, Kremlevskaya 18, Kazan, Russia
Doping with rare-earth (RE) ions makes the fluoride host materials useful for various
applications, such as lasers, phosphors, scintillators, superionic conductors. Investigations of
doped centers in the fluorite structure crystals Me1-xRExF2 (Me = Ca, Ba, Sr, Pb) is performed
for many years. The point symmetry in the positions substituted by the RE ions can be cubic,
tetragonal or trigonal [1]. Traditional methods of preparation of samples are crystal growth or
solid-state synthesis. Mechanochemical doping is an effective and economically sound way of
obtaining the RE-doped fluorides. This area is developing fast since year 2006; only few
papers have been devoted to the application of the magnetic resonance spectroscopy methods
to studies of the mechanically doped solids and, especially, crystalline fluoride powders [2].
In [3] the Er3+
paramagnetic centers in BaF2 and SrF2 single crystals have been studied and it
was shown that with an increase of a total Er3+
ion concentration (from 0.001 to 0.1 %) the
fraction of cubic centers decreased. In the present work we show that in Er-doped CaF2, BaF2,
SrF2 and nanopowders the cubic center pattern dominates in the EPR spectrum up to the
concentration of 10 wt.% of ErF3 in the initial mixture. On the other hand, in erbium-doped
PbF2 nanopowders cubic centers are also observed however the dominating RE-ion centers
are of the lower symmetry.
We report the results of the EPR study of the fluorite-based (CaF2, BaF2, SrF2)
nanopowders doped mechanochemically with erbium ions. All the materials reveal typical
well-defined EPR spectra of the cubic Er3+
centers near g = 6.78. Grain size dependences
show unambiguously that these centers concentration correlates with the amount of the
particle surface [4]. Moreover, in erbium-doped CaF2 nanopowder the cubic center pattern
dominates in the EPR spectrum up to the concentration of 10 wt.% of ErF3 in the initial
mixture.
Mechanochemical doping of the PbF2 nanopowders with Er ions differs in several
aspects from that of the other cubic fluorites. First, the EPR spectra of mechano-doped
PbF2:Er3+
reveal a signal of the cubic centers; however, the axial centers dominate in the
spectra. Another peculiarity of the EPR spectrum of Er-doped PbF2 nanopowder is an absence
of the dependence of doped centers concentrations on the particle size. This fact indicates that
during the mechano-doping of PbF2 nanoparticles with Er3+
ions the mechanism of the cubic
center formation differs from that occurring in the cases of CaF2, BaF2, and SrF2.
[1] L K Aminov, I N Kurkin Solid State Physics, 51, 4 (2009) [2] G Scholz, D Heidemann et.al., Journal of Solid State Chemistry 179, 1119–1128
(2006)
[3] A A Antipin, I N Kurkin, L D Livanova, L Z Potvorova and LY Schekun Solid State
Physics, 8, 9 (1966)
[4] I A Irisova, A A Rodionov et al. J. Phys.: Conf. Series 324, 012026 (2011)
203
PII_44 Ab-initio investigation of phonon spectra in GdLiF4 compound
under hydrostatic pressure
A. V. Petrova1)
, B. Minisini2)
, O. V. Nedopekin1)
, D. A. Tayurskii1)
1)Institute of Physics, Kazan Federal University, 420008, 18 Kremlevskaya st., Kazan, Russia
2)Institut Supérieur des Matériaux et Mécaniques Avancés du Mans, 72000, 44 Av.Bartholdi,
Le Mans, France
Because of their interest as laser host materials, a large number of doped or pure rare
earth fluoroscheelites (REF) have been synthesized during the last decades [1, 2]. The most of
experimental studies were focused on magnetic [3] or optical properties [4]. Recently it has
been recognized that pressure dependencies of fluorides optical properties are not still well
understood.
In the present work the theoretical studies of optical properties GdLiF4 compound was
carried out by using PHONON code [5] as implemented in VASP 5.2 [6], part of MedeA©*
modelling interface. These simulations based on the quantum chemistry method of Density
Functional Theory [7, 8]. The non-magnetic approximation was used as well as the
approximation where f-electrons of gadolinium ions are «kept frozen in the core». The lattice
vibrational properties of GdLiF4 were calculated within the harmonic approximation. In
PHONON module the force constant matrix was calculated via atomic displacements. The
phonon dispersion curves of GdLiF4 within a range from 0 to 12 GPa have been obtained. The
instability of the crystal structure appears starting with pressure 4 GPa (that could be seen
from the appearance of the «negative frequencies» in the spectrum). The dependencies of
optical modes (Raman and infrared modes) on pressure have been investigated and compared
with available experimental data.
References
[1] P.E. Hansen, T. Johansson, R. Nevald, Phys. Rev. B 12 (1975) 5315.
[2] S. Salauen, M.T. Fornoni, A. Bulou, M. Rousseau, P. Simon, J.Y. Gesland, J. Phys.:
Condens. Matter 9 (1997) 6941.
[3] P.E. Hansen, T. Johansson, R. Nevald, Phys. Rev. B 12 (1977) 146.
[4] I. Razumova, A. Tkachuk, A. Nikitichev, D. Mironov, J. Alloys Compd. 225 (1995) 129.
[5] K. Parlinski, Z.Q. Li and Y. Kawazoe Phys. Rev. Lett. 78 (1997) 4063.
[6] G. Kresse, J. Furthm¨uller Phys. Rev. B 54 (1996) 11169.
[7] P. Hohenberg, W. Kohn Phys. Rev. B 136 (1964) 864.
[8] W.Kohn, L. J. Sham Phys. Rev. A 140 (1965) 1133.
* Materials Design Angel Fire NM
204
PII_45 About Coulomb interaction in systems with the delocalized electrons
O.A. Anikeenok
Kazan Federal University, Kremlyovskaya 18, Kazan, 420008 Russia
In previous paper [1], considering effects of nonorthogonality electronic orbital’s in a crystal,
I suggested the following expression for Hamiltonian
1 1. .
2 2
bm f
b b
nH a a a a b b g h c
r R,(1)
where ( )a a
is a creation (annihilation) operator of electron of a chosen ion, ( )b b
operators correspond to electron of surrounding crystal lattice; 1
I S
, I - a
unit operator, S is a matrix, constracted from overlap integrals of one-electron orbitals. The
second item in (1) contains the contribution that exactly compensate first one in limit of large
distance bR . Or in other words m fH is Coulomb interaction operator of electrons of a chosen
ion with the all surrounding electrons shells of crystal lattice. In the present comunication I
want to concretize the method of calculation of matrix elements:
1 2 1 2 1 2
1 2
1
n n b a
dV dV
R
r r r rr r R r r
, (2)
Here the summation over nR means the summation on unit cells; the radius-vectors ,a br r
refer to corresponding ion position in unit cell. Let us take the radial part of radial wave
function as 2expl
nl i iR a r r . Then we have found that the integrals (2) can be
expressed through the functions
3
2 2 331 2
0 1 0 031 2
1 ! !4 11
2 !
s ss s
s s s s
s s ss
s s
n p n mw n m ms s s
a b i k j l p w wns m wc ik jl s s
nn n p n pF a a b b C C
pp p v n m
g
(3)
22
2
20
exp4
! 2 ,! !
ss s s s
b a
s
ik jlmh m m h
ik jlik jl ik jl i
s s s s s
h s s s
n h f n h g eh m h
g r r
g
g
where cv is the unit cell volume, ik i k ; g is the reciprocal lattice vector, 1 ,xg g
2 ,yg g 3 zg g ; sn , sp - integral numbers; n
mC -binomial coefficient; functions , sf n g
were determined in [2.3].
The expression (3) can be easily computed and used for the calculations of density-density
contribution in crystal field parameters, to the energy orbital ordering and for improvement of
tight binding approach.
[1] O.A. Anikeenok. Phys. Solid State 47, 1100 (2005).
[2] O.A. Anikeenok. Magn. Res. Solids. Electron. J. 13, 27 (2011).
[3] O.A. Anikeenok. Phys. Solid State 54, 1847 (2012).
205
PII_46 Paramagnon-like excitations theory for magnetic properties of layered
copper oxide superconductors as obtained by resonant inelastic X-ray scattering
I.A. Larionov1,2)
1) Kazan Federal University, Kremlevskaya 18, 420008 Kazan, Russia
2) National University of Science & Technology "MISIS", 119049, Moscow, Russia
E-mail: [email protected]
Using a relaxation function theory we obtain and analyze the dynamic spin
susceptibility expressions for doped S=1/2 two-dimensional Heisenberg antiferromagnetic
(AF) model in the paramagnetic phase taking into account the thermal damping effects of spin
wave-like (paramagnon-like) excitations. The relaxation function theory is widely applicable
for describing the properties of nonequilibrium systems and by itself the Markovian situation
can be valid even in the absence of any picture of the system in terms of well-defined
excitations [1]. The presentation is valid for all wave vectors throughout the Brillouin zone.
The role of damping (lifetime) of paramagnon-like excitations, its evolution with
doping and temperature, is highlighted in view of magnetic response of high-Tc layered
cuprates. It is shown [2] that the theory is able to explain the main experimentally observed
features in the imaginary part of the dynamic spin susceptibility in La2-xSrxCuO4 and
YBa2Cu3O7- as obtained by resonant inelastic X-ray scattering (RIXS) [3]. The calculated
dynamic spin susceptibility [4] gives a reasonable agreement together with neutron scattering
experiments [5] and nuclear spin-lattice relaxation rates 1/T1 [6] data from pure AF insulator
right up to optimally doped high-Tc’s in the normal phase.
We emphasize the importance of short-range AF order, its temperature and doping
dependence, on dynamic spin susceptibility for magnetic properties of layered copper oxide
superconductors as obtained by RIXS.
Fig.1. Dispersion of paramagnon-like excitations along the (0,0)-(π,0) axis as obtained by resonant
inelastic X-ray scattering (RIXS). Experimental data at Т = 15 К are taken from [4]. Solid lines show
calculations with damping of paramagnon-like excitations. Dashed lines show calculations results
without damping.
1. U. Balucani, M. H. Lee, and V. Tognetti, Phys. Rep. 373, 409 (2003).
2. I.A. Larionov, to be published.
3. M. Le Tacon et al., Nature Physics 7, 725 (2011)
4. I.A. Larionov, Phys. Rev. B 69, 214525 (2004); 72, 094505 (2005); 76, 224503 (2007)
5. B. Keimer et al., Phys. Rev. B 46, 14034 (1992).
6. T. Imai, C. P. Slichter, K. Yoshimura, and K. Kosuge, Phys. Rev. Lett. 70, 1002 (1993).
206
PII_47 NQR, NMR and high field ESR investigation
of the magnetic order in InCu2/3V1/3O3
E. Vavilova1)
, M. Yakovleva1)
, M. Yehia2)
, V. Kataev2)
, T. Taetz3)
,
A. Moeller4)
and B. Buechner2)
1)
Zavoisky Physical Technical Institute, RAS, Kazan, Russia
2) IFW Dresden, Dresden, Germany
3) Institut fur Anorganische Chemie, Universitaat zu Koln, Germany
4) University of Houston, Department of Chemistry and Texas Center for Superconductivity
We study new quasi two-dimensional spin-1/2 honeycomb lattice compound InCu2/3V1/3O3
with high field electron spin resonance, nuclear magnetic resonance and magnetization
methods. Uncorrelated finite size structural domains occurring in this honeycomb planes are
expected to inhibit long range magnetic order. Surprisingly, magnetic resonance data show
the development of two coollinear antiferromagnetic (AFM) sublattices below 35 K and the
presence of the staggered internal field. Magnetization data evidence a spin reorientation
transition at 5.7 T. ESR, NMR and NQR data allow to retrace the development of staggered
magnetization during the crossover to ordered ground state.
The mechanism for setting of the antiferromagnetic order with NQR method was
investigated. The derived model of the antiferromagnetic sublattices describes the results of
NMR and NQR experiments.
207
PII_48 EPR and ENDOR study of charge-compensated Fe3+
centers in ZnO
Yu. S. Kutin, G. V. Mamin, S. B. Orlinskii
Kazan Federal University, 420008, Kremlyovskaya St.18, Kazan, Russia.
e-mail: [email protected]
Theoretical prediction of a high Curie temperature in ZnO doped with Mn, Co, Fe, and
other transition metals has stimulated the investigation of these materials by many research
groups. Although charge-compensated Fe3+
centers in ZnO:Fe have been observed by means
of EPR and have been known for decades, conclusions on the chemical nature of these defects
are still contradictory. Originally, these centers were treated as Fe3+
-Li+ complexes with both
ions occupying adjacent cationic position [1]. Recently, however, the centers were interpreted
as a substitutional Fe3+
ion with a vacancy at an adjacent zinc or oxygen site (Fe-VZn or Fe-
VO) [2]. In order to conclusively determine the chemical nature of these complexes, electron-
nuclear double resonance (ENDOR) spectroscopy was used in the present work.
Fig.1 (left) shows the EPR spectrum of a hydrothermally grown ZnO crystal for B || c.
Fifteen EPR lines are grouped into three fine-structure quintets originating from three types of
charge-compensated Fe3+
centers (labeled C1, C2 and С3), each with the electron spin
S = 5/2. Fig.1 (right) shows three ENDOR spectra recorded in the 1/2 EPR transitions
of each center. The ENDOR spectra reveal NMR transitions corresponding to a nucleus with
g-factor gN = 2.171 and spin I = 3/2. This unambiguously shows presence of Li as a charge
compensator. Both Fe and Li substitute Zn ions at two adjacent cationic sites of ZnO.
Depending on the relative positions of the two impurity ions in the hexagonal lattice, three
kinds of Fe3+
-Li+ complexes are formed.
As seen in Fig.1 (right), the hyperfine and quadrupole interaction strongly depend on the
particular arrangement of the Fe-Li complex. The electric field gradients at the 7Li nuclei
were estimated to be at least 5 times lower than at undistorted Zn sites.
References
[1] W.C. Holton, M. de Wit, T.L. Estle, et al., Phys. Rev. 169, 359 (1968)
[2] D.V. Azamat, M. Fanciulli, Physica B, 401–402, 382 (2007)
Fig.1. (left) EPR spectrum of a ZnO single crystal for B || c. T = 20 K, f ~ 93.9 GHz. The 30 lines near g ~ 2
originate from Mn2+ and the five high-intensity lines correspond to Fe3+. Three fine-structure quintets
originating from the charge-compensated Fe3+ centers are indicated. (right) ENDOR transitions of the 7Li
nuclei recorded in the 1/2 EPR transitions of the three charge-compensated Fe3+ centers.
208
PII_49 Submillimeter EPR spectroscopy of the Cr2+
ions in KZnF3 crystal
S.I. Nikitin1, G.S. Shakurov
2, T.R. Sharafiev
1, V.F. Tarasov
2, R.V. Yusupov
1, D.G. Zverev
1
1) Kazan Federal University, Kremlevskaya 18, 420008 Kazan, Russia
2) Zavoisky Physical-Technical Institute RAS, Sibirsky Trakt 10/7, 420029 Kazan, Russia
e-mail: [email protected]
Spectroscopy of the Jahn-Teller (JT) Cr2+
ions substituting for the perfect octahedrally
coordinated crystal sites with the cubic symmetry has a long history. The ground state is the
orbital doublet 5Eg which is coupled strongly to the lattice. Therefore spectral lines are very
broad and special methods like acoustic paramagnetic resonance [1] and thermal conductivity
measurements [2] had been applied for investigation of the low-energy level structure.
However, the obtained results had not provide the researchers with the comprehensive
information on the vibronic and spin-orbit interaction values as well as the influence of the
random strains on the Cr2+
ion ground state. Since the splittings between the ground state
energy levels are of the order of 1 - 10 cm-1
the submillimeter EPR spectroscopy is a
convenient tool for these studies. There is only one publication devoted to the spectroscopy of
the Cr2+
ions in this wavelength range [3]. However, the interpretation of the observed spectra
in [3] is ambiguous.
In our report the results of the submillimeter EPR studies of the Cr2+
ions in KZnF3 crystal
will be presented. KZnF3 crystal has the cubic perovskite structure and is convenient host
lattice for investigations of the Cr2+
ions in the octahedral surrounding.
EPR spectra were measured with the homemade wideband quasi-optical EPR
spectrometer. In the spectra of the KZnF3:Cr2+
crystal two groups of lines are observed at
227 GHz and 78 GHz in zero magnetic field. These lines have the strong angular dependence
revealing the tetragonal symmetry of the center. Observed spectra were described with an
axial-symmetry spin-Hamiltonian for with ≈ cm-1
and ≈ . Thus the
lines at 227 GHz and 78 GHz were assigned to the transitions | ⟩ | ⟩ and | ⟩ | ⟩, respectively.
Tetragonal symmetry of the Cr2+
center in KZnF3 crystal is a manifestation of the static JT
effect. Transition from the dynamic to static JT effect as well as the broad asymmetric EPR
line shapes occur due to the presence in the crystal of the random strains. The simulations of
the EPR spectra were performed within the frames of the model proposed by Fletcher and
Stevens [4] with the tunneling splitting value obtained in [5] and different distributions of the
strains. The simulations have shown that the consistent description of both the submillimeter
EPR and optical data [5] is achievable only with random strain distribution [6]
3
2 2 2
( ) .s
s
Af e
e w
This, in turn, indicates that the random strains in the studied sample originate from the point
defects [6].
1. S. Guha and J. Lange, Phys. Rev. B 15, 4157 (1977)
2. L.J. Challis et al, Proc. R. Soc. A 330, 29 (1972)
3. C.G.C.M. de Kort et al, J.Phys. C: Solid State Phys. 13, 1305 (1980)
4. J.R. Fletcher and K.W.H. Stevens, J. Phys. C: Solid State Phys. 2, 444 (1969)
5. I.N. Gracheva, S.I. Nikitin and R.V. Yusupov, J. Phys.: Conf. Ser. 324, 012030 (2011)
6. V.Ya. Mitrofanov et al., J. Magn. Magn. Mater. 36, 26 (1983)
209
Author list
A.M. Abdrakhmanov
R.D. Aglyamov
V.M. Agranovich
R.A. Akhmedzhanov
O.R. Akhtyamov
E.M.Alakshin
H. Alloul
G. Alombert-Goget
D. Amans
L.K. Aminov
N.V. Andreev
S. I. Andronenko
L.A. Andryushenko
A.E. Angervaks
O.A. Anikeenok
Ž. Antić
S.A. Antoshkina
M.Yu. Artyomov
H. R Asatryan
A . Aubret
К.S. Avadov
N.S. Averkiev
E.I. Baibekov
A. Baniodeh
A.N. Baranov
P.G. Baranov
B. Barbara
K. Bartosiewicz
K.A. Baryshnikov
N. Basavaraju
T.T. Basiev
L.E. Bausá
E. I. Beliakova
K. N. Belikov
A. Belsky
M. Berkowski
I.B. Bersuker
A. Bessière
M. Bettinelli
L.N. Bezmaternykh
M. Bieza
T.B. Biktagirov
D.A. Bizyaev
A.I. Bobrov
K.N. Boldyrev
A.A. Bondartsev
A.V. Boris
T. Borzda
R. Böttcher
G. Boulon
V. Boyko
D. Brida
PI_29
PI_38
We-3
Mo-9
TuII-17
Fr-1 PII_12
TuI-8
TuII-11
PI_45
PII_14 PII_17
Fr-4
PII_18
PI_18
PI_15 PI_16 PI_50
PII_45
PI_44
Th-12
PII_3 PII_4
TuII-3 PII_19
PI_45
PII_33
Mo-7
We-7 PII_15
PII_5 PII_6 PII_7
TuI-4 PII_38
TuII-3
We-6 PII_15
TuII-4
Mo-7
Fr-5
TuII-7
Th-7
PI_37
PI_17
TuII-10
TuII-5
Mo-7
Fr-5
PI_42 PI_46
TuI-10 PI_6
TuII-4
PII_20
PII_37
Tu1-16
TuI-10 PI_6
Mo-9
TuI-5
TuI-18
PII_17
TuII-4 TuII-11 We-1
PI_23
PI_2
TuI-18
M.G. Brik
B. Buechner
A.A. Bukharaev
L. Caillat
D. Caurant
G. Cerullo
V.A. Chernyshev
V. I. Chichkov
V. Chornii
E.P. Chukalina
O.V. Chukova
V.N. Churmanov
J.M. Clemente-Juan
E. Coronado
S. David
J. Deisenhofer
A. Dejneka
E.S. Demidov
G.S. Denisov
Yu. Deshko
A.J. Dmitriev
Yu.K. Dolgikh
N.E. Domracheva
A.V. Dooglav
M.E. Doroshenko
M.D. Dramićanin
M. Dressel
A.M. Dubovik
C. Dujardin
E.B. Dunina
Yu.P. Efimov
V.N. Efimov
N.N. Efimov
N. L. Egorova
A.V. Egranov
S.A. Eliseev
T. Epicier
M.V. Eremenko
M. V. Eremin
R.M. Eremina
V.L.Ermolaev .
V.O. Erofeev
L. Esposito
M.L. Falin
I.I. Fazlizhanov
P.P. Fedorov
L. Fels
S.P. Feofilov
A. Ferrier
F. Fischgrabe
A.V. Fokin
L.A. Fomicheva
G. Fountos
PII_24
PII_47
PII_37
Mo-3
We-4 PI_41
TuI-18
Fr-9 PI_24
Fr-4
PI_2 PI_3
PII_16
PI_26 PI_27
TuI-4 PII_38
Mo-4
Mo-4
PI_22
TuI-9
TuI-14 PI_32 PI_47
Tu1-16
PII_41
We-5
PI_20 PI_36
We-8
PI_49
PII_23
TuII-7 PI_43
Th-10 PI_44
TuI-11
PI_18
PI_45
TuII-8 Th-3
We-8
PI_38
PII_9
PI_17
Fr-8
We-8
We-1
Fr-6 PI_36 PI_37
PII_39
Fr-4 PII_5
PI_31
PII_40
We-1
PII_25 PII_26
Fr-4
PI_15 PI_50
TuI-2
Th-5
Mo-10
TuI-11
PII_3 PII_4
Th-3
PI_22
210
Ch. Gadermaier
M.R. Gafurov
R.R. Gainov
R.V. Gainutdinov
A. Gaita-Ariño
O.M. Gaitko
V.R. Galakhov
R. Galeev
T.P. Gavrilova
R.R. Gazizulin
M. George
A. Georges
A.S. Gerasimenko
K.I. Gerasimov
L.R. Gilyazov
B.A. Gizhevskii
N.A. Glushkov
S.L.Gnatchenko
Ph. Goldner
V.A. Golovanevskiy
N.V. Golubev
L.E. Gonchar A.D. Gorlov
A. Gorokhovsky
V. G. Gorieva
B. Gorshunov
T. Goto
J.-L. Le Gouët
D. Gourier
M. Grinberg
M. Grüninger
M.S. Gruzdev
N.B. Gruzdev
I.A. Gudim
V.V. Gudkov
K.N. Guliaeva
L.A. Gushchin
Y. Guyot
M. Guzik
B. Hajj
B. S. Ham
J. Hanuza
M. Hedges
K. Hermanowicz
V.V. Hizhnyakov
Yu. Hizhnyi
J. Houel
D. Hreniak
R.B. Hughes-Currie
V.V. Iglamov
A. Ikesue
I A Irisova
A.V. Ishchenko
TuI-18
PII_14 PII_15 PII_20
PII_40
PII_23
PI_15
Mo-4
Th-12 PI_39 PI_40
PI_25
PII_5
Fr-4
Fr-1 PII_12
Mo-11
TuI-1
TuII-7
PII_25 PII_37
TuI-12 TuI-14 PI_47
PI_25
PI_30
PI_4 PI_7
Mo-10
PII_23
TuII-2
PI_1 PII_13
We-5
TuII-16
TuI-11
TuII-11 We-1
Mo-13
Fr-5
Th-9
TuI-2
Fr-3
TuI-4 PII_38
PI_4 PI_5 PI_7
Mo-7
TuII-15
Mo-9
TuII-4 TuII-11 PI_23
TuII-4 TuII-11 We-1
PI_23
Mo-3
Mo-8
TuI-15
Mo-11
TuI-15
Mo-5
PI_2 PI_3
PI_45
TuII-1
Th-14
PII_39
We-1
PII_43
Th-13
A. Ito
V.Yu. Ivanov
V.Yu. Ivanov (UFU)
T.A. Ivanova
G.I. Ivanova
K.V. Ivanovskikh
J. Iwańska
L. Jastrabik
M. Jelinek
H. Jelinkova
M.F. Joubert
I.S.Kachur
L.S. Kadyrov
F. Kajzar
N. Kalyvas
I. Kandarakis
A.Ya. Karasik
J. Karlsson
T. Kärner
M. Kashchenko
V. Kataev
B.N. Kazakov
B. Keimer
N.M. Khaidukov
G. Khaliullin
A.A. Khamzin
B.M. Khasanov
A.V. Khilko
T.G. Khottchenkova
M.M. Kidibaev
Yu.E. Kitaev
V.V. Klekovkina E.S. Klimashina
S. Klimin
G. Klingelhöfer
A.V. Klochkov
I.V. Kochubey
M. Koichi
A.A. Konovalov
V.A. Konyushkin
D.V. Konyushkin
O.V. Koplak
S.L. Korableva
A.A. Kornienko
T.S. Koroleva
L.F. Koryakina
L.S. Kostina
N.O. Kovalenko
Yu.V. Kozhanova
D.D. Kramushchenko
A. Krasnikov
R. Kremer
TuII-11
Th-1
TuI-4 Th-13
PII_9
PII_9
Th-14 TuII-18 PI_46
TuII-4
PI_32
TuII-7
TuII-7
TuII-18
PI_4 PI_7
TuI-11
PI_21
PI_22
PI_22
PI_43
Mo-14
PII_24
Th-4
TuI-7 PII_47
PII_36
TuI-5
Th-15 PI_10 PII_26
TuI-6
PII_30
PII_8
We-8
TuII-2
Th-13 PII_41
TuI-15
PII_21 PII_23 PII_20
Th-4
PII_23
Fr-1 PII_12
PII_34
TuII-11
PII_10
PI_43
PI_43
PI_20 PI_36
TuII-14 TuII-16 TuII-
18 Fr-1 PI_13 PI_35
PI_38 PI_48 PII_12
PII_35 PII_36
TuII-8 Th-3
Th-13
PI_16
PI_37
TuII-7
PI_36
TuII-3
TuII-9
TuI-11
211
S. Kröll
V. Ksenofontov
T.A.Kudykina
N.A. Kulagin
F. Kulzer
I.N. Kurkin
Yu.S. Kutin
T.V. Kutsak
A.M. Kuzmenko
R.V. Kuzmin
U. Kynast
S.Lange
I.A. Larionov
A.L. Larionov
T. Larkin
V.A. Latypov
K. Lebbou
G. Ledoux
J. Legendziewicz
I.I. Leonidov
A.M. Leushin
M. Lezhnina
P. Liaparinos
H. Linget
R. Lisiecki
V.N. Lisin
V. M. Lisitsyn
A.G. Litvak
A. Loidl
P.H.M. van Losdrecht
N.N. Loshkareva
A. Louchet-Chauvet
A.V. Lovchev
K.A. Lyssenko
C.-G. Ma
M. Mączka
V.N. Makhov
T.I. Maksimova
A.V. Malakhovskii
G.E. Malashkevich
N.V. Malekhonova
B.Z. Malkin
H. Mallazadeh
A.V. Malov
E.Kh. Mamadzhanova
D.V. Mamedov
G.V. Mamin
C. Manzoni
L. Marciniak
D. van der Marel
M. Marinović-Cincović
M A. Marisov
Mo-14
PII_23
PII_31
Th-8
PI_45
Fr-2 PII_13 PII_14
PII_15 PII_17
PII_48
PI_5
Th-1
PI_37
TuI-17
PI_40
PII_46
PII_42
TuI-5
PII_25 PII_26
Th-13
PI_45
PI_23
Fr-9 PI_34
PII_25
TuI-17
PI_22
Mo-13
TuII-5
Fr-10
PI_18
Mo-9
TuI-9
Th-4
Fr-7
Mo-13
PI_38
PI_21
PI_40
TuI-15
Th-15 PI_10
TuI-15
PI_4 PI_5 PI_7
TuII-2
Tu1-16
PI_42 PII_21 PII_22
PII_28
Mo-11
Th-12
TuII-2
Fr-4
PII_20 PII_40 PII_48
TuI-18
TuII-1
TuI-1
PI_44
TuII-13 TuII-16
TuII-17 PI_14 PI_38
V.Yu. Mayakin
A. Meijerink
M.A. Melkozerova
C. de Mello Donegá
T. Mertelj
V.V. Mesilov
A.Yu. Mester
M.M. Mezdrogina
Ch. Michail
S.A. Migachev
D. Mihailovic
L.V. Mingalieva
B. Minisini
L.Yu.Mironov
N. Mironova-Ulmane
S.K. Misra
A. Moeller
S.A. Moiseev
P. Molina
A.M. Monakhov
O.A. Morozov
V. Moshnyaga
A.S. Moskvin
E.V. Mostovshchikova
E.A. Motovilova
M. R. Muftakhutdinov
I.R. Mukhamedshin
A.A. Mukhin
Ya. M. Mukovskii
I. E. Mumdzhi
D.F. Nabiullin
A.N. Nakladov
A. Nalepa
A.K. Naumov
S. Nedilko
O. V. Nedopekin
R.R. Nigmatullin
A.E. Nikiforov
S.I. Nikitin
T. Nikolaenko
M.G. Nikolić
A.S. Nizamutdinov
A.A. Nugroho
L.A. Nurtdinova
D. Oblak
I.N. Ogorodnikov
S.I. Omelkov
S.B. Orlinskii
E.O. Orlovskaya
Yu.V. Orlovskii
V.V. Osiko
Mo-7
We-2 Th-14
PI_34
We-2
TuII-12
PI_25
PI_19
Fr-6 PI_20 PI_36
PI_37
PI_22
TuI-13
TuI-18 TuII-12
PII_9
PII_44
PI_31
PII_24
PII_18
PII_47
Mo-12
Th-7
Mo-7
PI_38
TuI-11
TuI-3
Fr-7.
TuI-11
PI_29
TuI-8
Th-1
Fr-4
PI_48
PII_22
PI_43
PII_18
PI_35 PI_38 PII_35
PI_2 PI_3 PI_26
PI_27
PII_44
PII_30
Fr-9 PI_1 PI_24
TuI-12 TuI-14 PI_47
PI_48 PII_49
PI_2
PI_44
TuII-13 TuII-17
PI_38
Th-4
TuII-14 TuII-18 PI_13
Mo-11
Th-13
TuI-4
PII_20 PII_40 PII_48
PI_39 PI_40
Th-11 PI_39 PI_40
TuII-7 PI_43
212
I.V. Ovchinnikov
V.V. Ovsyankin
A. Palii
A.A. Panov
V.V. Pavlov
E.D. Pavlova
C. Pedrini
I.S. Pekareva
F. Pellé
I.N. Pen’kov
M. J. Percino
T. Perova
A.I. Pervak
Á. Péter
V.P. Petrov
V.L. Petrov
V.V. Petrov
M.A. Petrova
A.V. Petrova
F. Piccinelli
A. Pillonnet
A. Pimenov
V.G.Piryatinskaya
R.V. Pisarev
A. Pogrebna
N.K. Poletaev
K. Polgár
E. F. Polisadova
A.V. Popov
M.N. Popova
A. Pöppl
A. P. Potapov
Z .Potucek
A. K. Powell
U.Pracht
K.R. Priolkar
D. Pröpper
T. Prutskij
K.K. Pukhov
A. Punnoose
L.N. Puntus
V.A. Pustovarov
V.I. Putlayev
V.M. Puzikov
A.V. Pyataev
D.S. Pytalev
F. Rabouw
E.A. Radzhabov
R.M. Rakhmatullin
M.O. Ramírez
R.J. Reeves
M.F. Reid
J. Reul
R. Ricken
PII_9
We-8
Mo-4
Th-12
TuII-14 Fr-2 PII_36
Tu1-16
Th-13
PI_21
Mo-3
PII_23
PI_28
PI_28
PII_31
PI_33
Fr-9 PI_24
Th-13
We-8
PI_16
PII_44
PI_46
PI_45
Th-2
PI_4 PI_7
TuI-10
TuII-12
PI_32 PI_33
PI_33
PI_17 PI_18
Th-11 PI_39 PI_40
Mo-6 TuI-10 PI_6
PI_42 PII_16
PII_17
PII_3 PII_4
PI_32
PII_5 PII_6 PII_7
TuI-11
Fr-5
TuI-5
PI_28
Th-6 PI_11 PI_12
PII_18
PI_21
TuI-4 PII_38
PII_20
TuII-7
Fr-3
PI_41 PI_42
We-2
Th-16 Fr-8
TuII-14 Fr-2 PII_17
Th-7
Th-14
Th-14
TuI-2
Mo-11
L. Rippe
A.A. Rodionov
I.V. Romanova
N.N. Rosanov
N.R. Rudoman
J. Ruppen
P.A. Ryabochkina
W. Ryba-Romanowski
A.I. Ryskin
А.М. Sabitova
Т.R. Safin
К.R. Safiullin
G.M. Safiullin
E. Saglamyurek
A.J. Salkeld
M.N. Sarychev
V.P. Scherbatsky
M. Schmidt
S. Schweizer
I.N. Sedunova
S. K. Sekatskii
V.V. Semashko
T.S. Semenova
S. Sen
T. Senden
D. Serrano
G.S. Shakurov
T. Shalapska
Yu.A. Shafir
T.R. Sharafiev
G. L. Sharipov
S.K. Sharma
A.S. Shcheulin
A.M. Shegeda
V.P. Sheludko
R.Y. Shendrik
S.A. Shnaidman
B.V. Shulgin
V. Shynkar
V.N. Sigaev
I. Sildos
N. Sinclair
A.M. Sinitsyn
A. Sirenko
A.P. Skvortsov
V. Skvortsova
J.A. Slater
M. Slobodyanik
S.N. Smirnov
Mo-14
TuI-14 Fr-4 PII_12
PII_14 PII_20 PII_27
PII_43
PII_28
Mo-2
PII_32
TuI-1
Th-12
TuII-5
PI_15 PI_16 PI_50
Fr-1 PII_12
Fr-1
Fr-1 PII_12
PI_14
Mo-11
Th-14
Mo-7
PI_27
TuI-9
PII_25
Th-13
Mo-15 PI_11 PI_12
TuII-13 TuII-14 TuII-
16 TuII-17 TuII-18 Fr-
2 PI_13 PI_14 PI_38
PI_16
PII_17
We-2
Mo-14
TuI-12 TuI-13 PII_11
PII_19 PII_49
TuII-9
PI_20
PII_49
PI_29
Fr-5
PI_15 PI_16 PI_50
Fr-10
PI_2 PI_27
Fr-8
TuII-13
Th-13
Mo-3
TuII-2
Th-11 PI_39 PI_40
PII_24
Mo-11
PII_1 PII_2
PI_6
PI_32 PI_33
PII_24
Mo-11
PI_2
Fr-6
213
D.A. Sobgayda
W. Sohler
V.I. Sokolov
P.S. Sokolov
A.E. Sokolov
V.I. Solomonov
N. K. Solovarov
O.V. Solovyev
J.-M. Spaeth
A.V. Spirina
T.N. Stanislavchuk
W. Strek
B.V. Stroganov
A.Yu. Strokova
A. Strzęp
G. Stryganyuk
K.A. Subbotin
М.V. Sukachev
A.A. Sukhodola
A.L. Sukhachev
A. Sukhanov
Yu.P. Sukhorukov
L.L. Surat
E.B.Sveshnikova
P.P.Syrnikov
T. Taetz
M.S. Tagirov
H. Takagi
T. Takayama
V.F. Tarasov
O.A. Tarasova
D A Tayurskii
A.N. Tcherepanov
A.V. Telegin
V.L.Temerov
K. Terebilenko
E.I. Terukov
J. Teyssier
A. Thurber
W. Tittel
E. Tomaszewicz
P. Tomaszewski
P. Topolovsek
V.I. Torgashev
I.N. Trapeznikova
V.A. Trepakov
M. Trevisani
J.-M. Triscone
A.N. Trofimov
A.A. Tronov
M. Trubitsyn
D.I. Tselischev
E.Yu. Tselischeva
Mo-9
Mo-11
TuI-4 PII_38
TuI-4 PII_38
PI_4 PI_5
PII_29
PII_37
PI_8 PI_9
PII_25
PII_29
PI_6
TuII-1
We-8
PI_5
TuII-5
TuII-9
PII_10
PII_33 PII_34
TuII-2
PI_4 PI_5 PI_7
PII_5 PII_6 PII_7
PII_9
Fr-7
PI_34
PI_31
PII_27
PII_47
Fr-1 PII_12 PII_28
TuI-5
TuI-5
TuI-12 PII_10 PII_49
PI_34
PII_43 PII_44
Th-13
Fr-7
PI_4 PI_5
PI_2
Fr-6 PI_36
TuI-1
PII_18
Mo-11
PI_23
PI_23
TuI-18
TuI-11
PI_20
TuI-14 PI_32 PI_47
PII_27
PI_46
TuI-1
TuII-15 PI_19
Tu1-16
PI_3
PI_35 PI_38 PII_35
PI_35 PI_38 PII_35
B.S. Tsukerblat
V. Tsurkan
A.A. Tukhbatullin
Е.N. Tumayev
I. A. Tupitsina
O.A. Turanova
A.P. Tyutyunnik
V.A. Ulanov
S.N. Ushakov
F.G. Vagizov
I. Valais
D.T. Valiev
A.S. Vanetsev
E. Vavilova
V.A. Vazhenin
B. Viana
L.V. Victirov
A. Ja. Vinogradov
S.V. Virko
Yu.V. Vladimirtsev
I. Volnyanskaya
A. Voloshinovskii
V.E. Vorobeva
V. Voronkova
E.G. Vovkotrub
Z. Wang
J.-P.R Wells
Z.A. Xu
M. Yakovleva
A.G. Yakubovskaya
Y. Yan
A. N.Yaresko
I. N. Yassievich
I.V. Yatsyk
B.V. Yavkin
M. Yehia
A. Yoshikawa
E. Yraola
R.Yu. Yunusov
A.N. Yunusova
R.V. Yusupov
Y.A. Zagoruiko
R.R. Zainullin
M.V. Zamoryanskaya
V.S. Zapasskii
S. Zapf
S. Zazubovich
I.V. Zelensky
T. Zhang
Y. Zhao
E.V. Zharikov
I.V. Zhevstovskikh
E.R. Zhiteitsev
Mo-4
TuI-9
PI_29
PII_32 PII_33 PII_34
PI_18
PII_9
Fr-9 PI_34
PII_1 PII_2
Th-12
PII_23
PI_22
PI_17 PI_18
Th-11 Th-12 PI_39
PI_40
PII_47
PII_3 PII_4
Fr-5
Th-13
PI_20
PI_27
PII_37
PI_3
TuII-9
Fr-3
PII_5 PII_6 PII_7
Fr-9
TuI-9
Th-14
TuII-12
PII_47
PI_18
Mo-14
TuI-5
TuII-6
Fr-4
PII_20
PII_47
TuII-11 We-1
Th-7
PI_8 PI_9
PI_14
TuI-12 TuI-14 PI_47
PII_27 PII_43 PII_49
TuII-7
PII_1 PII_2
TuII-15 PI_19
Mo-1
TuI-11
TuII-9
Mo-9
TuI-11
We-2
PII_10
Mo-7
PII_1 PII_2
E. Zhukova
M.Z. Ziyatdinova
V.G. Zubkov
D.G. Zverev
TuI-11
TuII-2
Fr-9 PI_34
TuI-12 TuI-14 PII_12
PII_15 PII_27 PII_49
E. Zych
J. Zyss
TuII-4
Mo-3
![arXiv:cond-mat/0610708v1 [cond-mat.supr-con] 25 Oct 2006 · Bochum, Germany efetov@tp3.rub.de 2 L. D. Landau Institute for Theoretical Physics RAS, 119334 Moscow, Russia 3 Zavoisky](https://img.pdfslide.us/doc/110x75/5fc4da3e5cdfa15a9c414a80/arxivcond-mat0610708v1-cond-matsupr-con-25-oct-2006-bochum-germany-efetovtp3rubde.jpg)
