Abstract Book - inc.uam.es · Abstract Book . Science and Technology at High Magnetic Fields Miraflores de la Sierra, Madrid, 6-9 November, 2012 2 ... List of Participants ..... 67

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International Workshop

Science and Technology at High Magnetic Fields

“La Cristalera”, Miraflores de la Sierra, Madrid, 6-9 November (2012)

Abstract Book

http://www.nanobiomagnet.es/

Science and Technology at High Magnetic Fields Miraflores de la Sierra, Madrid, 6-9 November, 2012

2

Contents

Aims and Scope ..................................................... 3

Invited Speakers ................................................... 6

Venue and Travel Information ............................ 7

Program................................................................. 11

Abstracts of Lectures ........................................... 17

Abstracts of Posters ............................................ 47

List of Participants ............................................. 67

Miraflores de la Sierra, Madrid, 6-9 November, 2012 Science and Technology at High Magnetic Fields

3

Aims and Scope

Aims and Scope

The objective of this workshop is to present a modern overview of science and

technology at high magnetic fields. The meeting will serve to establish the

needed technical coordination for future developments to perform experiments

at high magnetic fields. It will allow for a more effective participation of Spanish

laboratories in high magnetic field facilities. Users of high magnetic field

facilities, in particular young students and post docs, will be supported by

waiving the workshop's registration fee. Total amount of participants, including

invited lecturers is limited to 65.

The talks will cover:

Facilities for high magnetic field experiments.

Strongly correlated systems.

Heavy fermions.

Quantum phase transitions.

Graphene.

Topological insulators.

Cuprate superconductors.

Vortex lattice.

Iron pnictide superconductors.

Quantum dots.

Molecular materials.

High magnetic field Scanning Microscopies.

Magnetic fields for fusion and high energy physics.

Nanoscience

High magnetic fields for beamlines.

Bio-medical imaging.

Nuclear magnetic resonance.


4

Organizers

• Hermann Suderow (Chair)

• Isabel Guillamón (Vice Chair)

• Jose Gabriel Rodrigo

• Sebastián Vieira

• Mar García-Hernández

• Francisco Guinea

INTERNATIONAL COMMITTEE

• Jan Kees Maan (NMFL, Nijmegen)

• Geert Rikken (LNCMI, Grenoble)

• J. Wosnitza (HLD, Dresden)

• Manuel Ricardo Ibarra (UNIZAR-INA, Zaragoza)

• Agustín Camón (UNIZAR, Zaragoza)

• Javier Tejada (UB, Barcelona)

Secretary:

Manuela Moreno

E-mail: [email protected], [email protected]

LOCAL ORGANIZING COMMITTEE:

• Prasanna Kulkarni

• Manuel R. Osorio

• Roberto F. Luccas

• José Augusto Galvis

• Antón Fente

mailto:[email protected]



5

SPONSORS

The Workshop is funded by the following institutions and research programs:

Spanish Ministery for Research (MINECO)

http://www.mineco.gob.es/

European Magnetic Field Laboratory (EMFL)

http://www.emfl.eu/home.html

Universidad Autónoma de Madrid (UAM)

http://www.uam.es

With the collaboration of:

The Nicolas Cabrera Institute (INC)

http://www.nicolascabrera.es/index.php/en

Oxford Instruments (OI)

http://www.oxford-instruments.com/

http://www.mineco.gob.es/

http://www.emfl.eu/home.html

http://www.uam.es/

http://www.nicolascabrera.es/index.php/en

http://www.oxford-instruments.com/Pages/home.aspx


6

Invited Speakers

Invited Speakers

Pedro ALGARABEL

ICMA-CSIC, Zaragoza, Spain

Dai AOKI

CEA-France & IMR, Tohoku University, Japan

Pegor AYNAJIAN

Princeton University, USA

Alexandre I. BUZDIN

Université Bordeaux, France

Antony CARRINGTON

University of Bristol, UK

Amalia COLDEA

University of Oxford, UK

Eugenio CORONADO

Universidad de Valencia, Spain

Enrique DÍEZ

Universidad de Salamanca, Spain

Fabienne DUC

LNCMI, Toulouse, France

Inês FIRMO

Cornell University, USA

Luís GARCÍA-TABARÉS

CIEMAT, Madrid, Spain

Xavier GRANADOS

ICMAB-CSIC, Barcelona, Spain

Gaël GRISSONNANCHE

Université de Sherbrooke, Canada

Paco GUINEA

ICMM-CSIC, Madrid, Spain

Marcelo JAIME

NHMFL-LANL, Los Alamos, USA

Enno JOON

NICPB, Tallinn, Estonia

Philippe LEBRUN

CERN, Geneva, Switzerland

Liang LI

WHMFC, Wuhan, China

Jan Kees MAAN

NFML, Nijmegen, The Netherlands

Ziad MELHEM

Oxford Instruments, UK

Oliver PORTUGALL

LNCMI, Toulouse, France

Geert RIKKEN

LNCMI, Grenoble, France

Masashi TOKUNAGA

IMGSL-ISSP, Tokyo, Japan

Johan VANACKEN

INPAC, K.U. Leuven, Belgium

Valerii VINOKUR

ANL, Argonne, USA

Peter WAHL

MPI-FKF, Stuttgart, Germany

Jochen WOSNITZA

HLD, Dresden, Germany

Shunsuke YOSHIZAWA

Tokyo Institute of Technology, Japan


7

Venue and Travel Information

Venue and Travel Information

LA CRISTALERA RESIDENCE

La Cristalera residence (http://www.lacristalera.com/) is located in Miraflores

de la Sierra (www.mirafloresdelasierra.org), a pleasant mountain resort near

Madrid.

The residence is equipped with some sport facilities and a swimming pool.

Mountain hiking trails for all levels can be easily accessed from the residence.

Internet can be accessed through EduRoam system (www.eduroam.org/) and a

wifi network (crisuam), with free access, at the dining room and conference

room.

http://www.lacristalera.com/

http://www.mirafloresdelasierra.org/

http://www.eduroam.org/


8

TRAVEL INFORMATION

A bus service between Madrid-Barajas Airport to La Cristalera will be organized

for participants arriving Tuesday November 6 and departing Friday 9. Details will

be given through the web page and email.

Arrival by plane:

You can reach Miraflores by taxi from the airport but this is an expensive choice

(around 90.00 Euro, but please ask before for a price).

The information for the driver is:

Miraflores de la Sierra

Residencia "La Cristalera"

Carretera de Miraflores de la Sierra a Rascafría Km.10 (M-611) 28792, Miraflores de

la Sierra (Madrid).

Tell him to go through "autovía de Colmenar, M-607".

You can also take a taxi from the Airport to Plaza Castilla (approximate fare:

45.00 Euro) and then take a bus to Miraflores.

A good choice is taking Metro from Airport to Plaza Castilla and then a bus to

Miraflores. At the airport, take Metro (underground), Line 8 (pink) to "Colombia"

(3 stations). Transfer in Colombia to line 9 (purple) to "Plaza de Castilla" (3

stations). It should take about 25 minutes. You will find more info at the Metro

webpage (http://www.metromadrid.es/en/index.html). In any case you can

ask for a map of Metro for free when you buy a ticket.

Once you have reached Plaza Castilla there are a lot of bus stops between the two

big inclined towers. Only one (725) goes to Miraflores de Sierra. Search number

725 (Madrid - Pza Castilla to Miraflores de la Sierra, Bustarviejo). There you’ll find

a timetable of the bus 725 (top part from Monday to Friday and bottom part for

Saturdays, Sundays and public holidays indicated in Spanish as "Lunes a Viernes

Laborables" and "Sabados Laborables, Domingos y Festivos" respectively). The

trip to Miraflores de la Sierra takes approximately 60 minutes and departure is

approximately each 30 min from 6.45 a.m. till 23.15 p.m. Your stop is the next

after "Soto del Real". You can find further information (in Spanish) in

http://www.encolmenarviejo.es/transporte-publico/bus/linea-725.

Taxi from Pza. Castilla to Miraflores costs around 60.00 Euro.

One way ticket to Miraflores by bus 725 costs 5. 5 Euro.

http://www.metromadrid.es/en/index.html

http://www.encolmenarviejo.es/transporte-publico/bus/linea-725


9

Arrival by train:

Coming from the North, the train station is usually Chamartin. From Chamartin,

you can take the Metro (line 10: dark blue or line 1: light blue) to Plaza de Castilla.

If you arrive at Atocha, you can take the Metro (line 1: light blue, 13 stations) to

Plaza Castilla and follow the above mentioned instructions for the bus.

Arrival by car:

Take the highway M-40. If you come from the south, Portugal, or the Zaragoza

Highways, take direction North (N-I). If you come from the Burgos Highway (N-

I) take the direction M-607 Tres Cantos- Colmenar Viejo. Go out of the M-40 to

the M-607 Highway towards Tres Cantos-Colmenar viejo. When the Highway

ends (roughly 30 km) take the direction Miraflores. After 30 km you will reach

the village. Once there, follow the signs towards La Cristalera, or Puerto de la

Morcuera. One km outside the village you will find the entrance to the residence

on your left (but watch out for it since sign is not a big one and may be missed).


10

MADRID RELATED LINKS

In the case that you want more information about Madrid, here are some related

links that could be of interest to you:

TRANSPORTS INFORMATION SYSTEM OF MADRID

http://www.ctm-madrid.es/

TRAINS

http://www.renfe.es/

TOURIST INFORMATION OF MADRID

http://www.gomadrid.com/

http://www.aboutmadrid.com/

http://www.descubremadrid.com/en/index.asp/

MUSEUMS

http://museoprado.mcu.es/

http://www.museoreinasofia.es/

http://www.museothyssen.org/thyssen/

FILMS, SHOPS, BARS, TAPAS, ETC.

http://www.softdoc.es/

WEATHER INFORMATION

http://weather.yahoo.com/forecast/SPXX0050_f.html/

http://espanol.wunderground.com/global/stations/08221.html/

http://www.ctm-madrid.es/

http://www.renfe.es/

http://www.gomadrid.com/

http://www.aboutmadrid.com/

http://www.descubremadrid.com/en/index.asp/

http://museoprado.mcu.es/

http://www.museoreinasofia.es/

http://www.museothyssen.org/thyssen/

http://www.softdoc.es/

http://weather.yahoo.com/forecast/SPXX0050_f.html/

http://espanol.wunderground.com/global/stations/08221.html/


11

Schematic Program

Program

Tuesday 6 Wednesday 7 Thursday 8 Friday 9

8:30

Opening 8:35

9:00

Session I Session II (2) Session IV 9:00 Maan Aoki Lebrun

9:30 Wosnitza Carrington Duc 9:30 10:00 Rikken Grissonnanche García-Tabarés 10:00 10:30 Coffee Break 10:30 11:00 Portugall Buzdin Granados 11:00 11:30 Li Coldea Melhem 11:30 12:00 Tokunaga Vinokur Coronado 12:00 12:30 Jaime Vanacken Closure 12:30 13:00

Lunch

13:00 13:30 13:30 14:00 14:00 14:30 14:30

15:00 Session II (1) Session III

Departure

15:00 Guinea Wahl

15:30 Díez Aynajian 15:30 16:00 Coffee Break 16:00 16:30

Arrival Registration

Desk Opens

Joon Firmo 16:30 17:00 Algarabel Yoshizawa 17:00 17:30

Discussion session 17:30 18:00

Poster Session

18:00 18:30 18:30 19:00

Dinner

19:00 19:30 19:30 20:00 20:00 20:30

Welcome

Reception Dinner 20:30


12

Detailed Program

Wednesday, 7 November 2012

08:30-8:50 Opening

08:50-9:00 Introduction to EMFL J.C. Maan

EMFL Coordinator

9:00-13:00 Session I

High Magnetic Field Facilities

09:00 Nijmegen High Magnetic Field Laboratory J.C. Maan

Nijmegen

09:30 Research and infrastructure at the Dresden

High Magnetic Field Laboratory

J. Wosnitza

Dresden

10:00 The Laboratoire National des Champs

Magnétiques Intenses

G. Rikken

Grenoble

10:30-11:00 Coffee Break

11:00 Beyond 100 tesla: scientific experiments using

single-turn coils

O. Portugall

Toulouse

11:30

Progress of the pulsed high magnetic field

facility at Wuhan National High magnetic

Field Center

L. Li

Wuhan

12:00 Developments at pulsed high field laboratory

in ISSP

M. Tokunaga

Tokyo

12:30

Frustrated magnetism and spin transitions via

lattice magneto-strain measurements in

pulsed magnetic fields to 100 Tesla

M. Jaime

Los Alamos

13:00-15:00 Lunch


13

15:00-17:30 Session II (1)

Graphene and Magnetism at High Fields

15:00 Magnetic and pseudomagnetic fields in

graphene

F. Guinea

Madrid

15:30 Quantum phase transitions in graphene E. Díez

Salamanca


16:30 Soliton lattice phase of spin-peierls state E. Joon

Tallinn

17:00

Magnetic, magnetotransport and

magnetoelastic measurements performed

using high magnetic fields

P. Algarabel

Zaragoza

19:00 Workshop Dinner


14

Thursday, 8 November 2012

9:00-13:00 Session II (2)

Electron Correlated Systems at High Fields

09:00 Ferromagnetic superconductivity and

quantum criticality

A. Aoki

Grenoble

09:30 Quantum Criticality and the nature of iron-

based superconductivity

A. Carrington

Bristol

10:00 The upper critical field of a cuprate

superconductor

G. Grissonnanche

Sherbrooke


11:00

Non-uniform (FFLO) states and quantum

oscillations in superconductors and superfluid

ultracold fermi gases

A. Buzdin

Bordeaux

11:30

The interplay between the localized and

itinerat electrons in a frustrated

antiferromagnetic metal 2H-AgNiO2

A. Coldea

Oxford

12:00 Reentrant Superconductivity in

Nanopatterned Systems

V. Vinokur

Argonne

12:30

Propagation of magnetic avalanches and

emitted electromagnetic radiation in Mn12-Ac

under high field sweep rates

J. Vanacken

Leuven

13:00-15:00 Lunch


15

15:00-17:30 Session III

High Field Scanning Tunneling Microscopy

15:00 Symmetry breaking excitations in iron-

chalcogenide superconductors

P. Wahl

Stuttgart

15:30 Visualizing heavy fermions emerging in a

quantum critical Kondo lattice

P. Aynajian

Princeton


16:30

Determining the Electronic Broken

Symmetries in the Pseudo-Gap Phase of the

Cuprates by Intra-unit-cell Fourier Transform

STM

I. Firmo

Cornell

17:00

Scanning Tunneling Spectroscopy of Vortex

Core States in High-Tc superconductor

Bi2Sr2CaCu2Ox

S. Yoshizawa

Tokyo

17:30-18:00 Discussion session about high field experiments

18:00-20:00 Poster Session

20:00 Dinner


16

Friday, 9 November 2012

9:00-12:30 Session IV

High Fields for Large Facilities and Applications

9:00 Superconducting magnets and cryogenics

for the large hadron collider (LHC)

Ph. Lebrun

Geneva

9:30 High pulsed magnetic fields for neutron

diffraction

F. Duc

Toulouse

10:00

CIEMAT activities concerning high field

magnets for particle accelerators and power

applications

L. García-Tabarés

Madrid


11:00 High Temperature Superconducting Magnets:

from Bulks to Coils

X. Granados

Barcelona

11:30 Next generation of high field superconducting

magnets

Z. Melhem

Oxford

12:00 Magnetic Conductors and Superconductors

through Chemistry

E. Coronado

Valencia

12:00-12:15 Closing Remarks

12:30-13:30 Lunch

14:00 Bus departure to Airport Madrid-Barajas


17

Abstracts of Lecturers

Abstracts of Lectures


18

MAGNETIC, MAGNETOTRANSPORT AND MAGNETOELASTIC

MEASUREMENTS PERFORMED USING HIGH MAGNETIC FIELDS

Pedro A. ALGARABEL

Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza – CSIC, Facultad de

Ciencias, 50009 Zaragoza, SPAIN

E-mail: [email protected]

A summary of the different experiments performed by the magnetism group of the ICMA

by using high magnetic fields will be presented. Magnetization measurements in Re-based

double perovskites and in antiferromagnetic ReVO3 (Re= Y, Ho) single crystals will be

reported. In the first case we will study the origin of the non-integer value of the saturation

magnetization and in the second one we will report the temperature dependence of the

spin-flop transitions observed in YVO3 and the magnetic structure deduced from the

magnetization experiments for the Ho sublattice in HoVO3 compound. Regarding

magnetotransport measurements magnetoresistance measurements up to 42 Tesla in cold-

pressed Fe3O4 nanopowders and Hall-effect measurements up 30 Tesla in epitaxial thin

films of Fe3O4 will be discussed. From these measurements the ordinary Hall effect

contribution has been obtained and an effective electron density corresponding to 1

electron per f.u has been deduced. Finally we will report magnetostriction measurements

performed in CaxSr2−xFeReO6 double perovskites studying the field-induced phase

coexistence and in Co- and In- doped NiMnGa alloys in which we will discuss the structural

(ΔV/V) effects related to the martensitic transformation presents in these compounds.


19

FERROMAGNETIC SUPERCONDUCTIVITY AND

QUANTUM CRITICALITY

Dai AOKI

INAC/SPSMS, CEA-Grenoble, IMR, Tohoku University


Recent advances on ferromagnetic superconductors are presented. The superconductivity

coexists with the ferromagnetism, forming the spin-triplet state of Cooper pairs. One of the

most remarkable phenomena is that the superconductivity is reinforced by the magnetic

field, indicating Ising-type ferromagnetic fluctuations. The quantum criticality associated

with magnetic and Fermi surface instabilities is discussed.


20

VISUALIZING HEAVY FERMIONS EMERGING IN A

QUANTUM CRITICAL KONDO LATTICE

Pegor AYNAJIAN

Joseph Henry Laboratories and Department of Physics, Princeton University,

Princeton, NJ 08544 USA


In solids containing elements with f-orbitals, the interaction between f-electron spins and

those of itinerant electrons leads to the development of low-energy fermionic excitations

with a heavy effective mass. These excitations are fundamental to the appearance of

unconventional superconductivity and non-Fermi liquid behavior observed in actinide- and

lanthanide-based compounds. I will present scanning tunneling microscopy data on the

emergence of heavy fermion excitations and their correlations in a prototypical family of Ce-

115 heavy fermion compounds. I will show, at the atomic scale, the composite nature of these

heavy quasiparticles, which arises from quantum entanglement of itinerant conduction and

f-electrons and resolve their energy-momentum structure. Finally, I will address the

behavior of these heavy quasiparticles in proximity to a quantum critical point.


21

NON-UNIFORM (FFLO) STATES AND QUANTUM OSCILLATIONS IN

SUPERCONDUCTORS AND SUPERFLUID ULTRACOLD FERMI GASES

Alexandre BUZDIN

Institut Universitaire de France and LOMA, University Bordeaux I, 33405 Talence, France


A long time ago, it was predicted by Larkin and Ovchinnikov and Fulde and Ferrell that the

non-uniform superconducting state (FFLO state) must appear in the magnetic field acting

on the electron spins. We start with the discussion of the distinctive features of the Fulde-

Ferrell-Larkin-Ovchinnikov (FFLO) non-uniform superconducting state and review recent

experiments on the heavy fermion superconductor CeCoIn5 and layered organic

superconductors providing strong evidences in favor of FFLO phase observation. It is

demonstrated that in 2D (or quasi 2D) superconductors the FFLO state leads to an

appearance of a very special oscillatory – like dependence of the upper critical field versus

the field orientation.

Interestingly that in the superconductor-ferromagnet heterostructures the FFLO-like state

may results in the formation of the Josephson junction with a spontaneous phase difference.

The FFLO-type instability may be also expected in ultracold Fermi gases in magneto-optical

traps. In these systems it is caused not by the Zeeman interaction but by the tuning of the

population imbalance between two lowest hyperfine states of the atoms. We briefly discuss

the properties of such FFLO state and analyze the role the trapping potential confining the

condensate.


22

QUANTUM CRITICALITY AND THE NATURE OF

IRON-BASED SUPERCONDUCTIVITY

Antony CARRINGTON

HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, UK


An enduring question in the field of iron-pnictide superconductors is to what extent the

superconducting properties are linked to the structure of the Fermi surface. Issues include

the relevance or not of quasi-nesting and how the topology and orbital character of the

Fermi surface may, or may not, influence the structure of the superconducting energy gap.

Mostly, this last point means whether or not the gap has nodes or is fully gapped. In order to

answer these questions it is desirable to have accurate measurements of the full three

dimensional Fermi surface and the k-resolved strength of the many body correlation effects.

An additional question is to what extent does quantum criticality increase the pairing

strength and thus form the driving force behind the observed high Tc.

Here I will review our measurement of the de Haas-van Alphen effect in several series of

iron-pnictide superconductors: LaFePO, BaFe2(As1-xPx)2 and the ‘11’ compounds LiFeP and

LiFeAs, from which we are able to determine with high accuracy the bulk Fermi surface

topology and the sheet -specific mass enhancement factors. The results will be related to

information gained on the structure of the energy gap as determined by London penetration

depth and thermal conductivity measurements. For the BaFe2(As1-xPx)2 system I will review

the evidence that the maximum Tc coincides with a quantum critical point where there is a

very strong enhancement in the effective mass. I will argue that pairing in this system takes

place between these strongly mass-enhanced quasiparticles, and that the quantum critical

point lies beneath the superconducting dome – rather than being avoided as occurs in some

other systems.


23

THE INTERPLAY BETWEEN THE LOCALIZED AND

ITINERAT ELECTRONS IN A FRUSTRATED

ANTIFERROMAGNETIC METAL 2H-AGNIO2

Amalia COLDEA

Oxford University, Physics, Clarendon Laboratory, Oxford, UK


I will present experimental data on single crystals of the frustrated triangular metallic

antiferromagnet 2H-AgNiO2 in high magnetic fields (54T) using thermodynamic and

transport measurements. The localized d electrons are arranged on an antiferromagnetic

triangular lattice nested inside a honeycomb lattice with itinerant d electrons. When the

magnetic field is along the easy axis we observe a cascade of field-induced transitions,

attributed to the competition between easy-axis anisotropy, geometrical frustration and

coupling of the localized and itinerant system. The sytem is a good metal and shows

quantum oscillations. The Fermi surface is likely to be reconstructed by the magnetic order

but in high fields magnetic breakdown orbits are possible. The itinerant electrons are

extremely sensitive to scattering by spin fluctuations and a significant mass enhancement (~

3) is found.


24

MAGNETIC CONDUCTORS AND SUPERCONDUCTORS

THROUGH CHEMISTRY

Eugenio CORONADO, E. NAVARRO-MORATALLA,

E. PINILLA, J.P. PRIETO, H. PRIMA

Instituto de Ciencia Molecular, Universidad de Valencia (Spain)

References

[1] Coronado, E; Day, P. Chem. Rev.104, 5419 (2004); E. Coronado, E.; Galán-Mascarós, J.

R., J. Mater. Chem. 15, 66 (2005)

[2] Coronado, E.; Martí-Gastaldo, C.; Navarro-Moratalla, E.; Ribera, A; Blundell, S. J.;

Baker, P. J., Nature Chem. 2, 1031 (2010)


One of the current trends in materials science is to create complex materials exhibiting

multifunctional properties. A possible approach to reach this goal consists of building up

two-network solids from the suitable molecular fragments where each network furnishes

distinct physical properties. Magnetic conductors combining electrical conductivity, or even

superconductivity, with magnetism exemplify this concept [1,2]. In this talk we will show

that these materials can be chemically designed as crystals, composite heterostructures, thin

films, or monolayers.


25

QUANTUM PHASE TRANSITIONS IN GRAPHENE

Enrique DIEZ1, M. AMADO1,*, C. COBALEDA1, J.M. CERVERÓ1,

S. PEZZINI1,2, F. ROSSELLA2, V. BELLANI2, D. LÓPEZ-ROMERO3,

D. K. MAUDE4 & W. ESCOFFIER4.

1 Laboratorio de Bajas Temperaturas, Universidad de Salamanca, E-37008 Salamanca, Spain

2 Dipartimento di Fisica “A. Volta” and CNISM, Università degli studi di Pavia, I-27100 Pavia, Italy

3 CT-ISOM, Universidad Politécnica de Madrid, E-28040 Madrid, Spain

4 Laboratoire National des Champs Magnetiques Intenses, CNRS, Toulouse and Grenoble, France

Present address: (*)SNS-NEST & CNR, Piazza San Silvestro 12, 56127 Pisa, Italy

Relativistic and topological effects, as well as non-linear interactions and disorder, play a key

role to determine the unique properties of graphene. Experimental measurements have

revealed that electronic localization in graphene, in the quantum Hall regime, is not entirely

dominated by single-particle physics, but rather a competition between the underlying

disorder and the repulsive Coulomb interaction exists [1]. Indeed, the effect of interactions

near the plateau-plateau (PP) and plateau-insulator (PI) quantum phase transitions (QPT),

and in particular the role of multifractality, are not well understood at the moment. For

instance, at the Integer Quantum Hall transition short range interactions seem to be

irrelevant, in a renormalization group sense, at the critical point, (i.e. the critical exponent

for the localization length and the multifractal spectrum remain the same as in the non-

interacting problem). The 1/r long-range Coulomb interaction is relevant, however, and

should drive the system to a novel critical point.

To measure experimentally the critical exponent of these transitions, we have studied the PI

and PP QPTs in a wide temperature range (from 4 K up to 230 K) and at different gate

voltages (VG) in graphene [2,3]. In the case of the PI ν = −2 to ν = 0 transition we have

observed it up to 45 K, pointing out the robustness of the QPT and of the metal and

insulating phases. The critical exponent for this transition is consistent with the accepted

universal value for 2DEGs when the sample is doped away from the Dirac point (κ = 0.58 ±

0.01) but tends to the classical full percolation limit (ν = 0.697 ± 0.005) when VG approaches

the charge neutrality point (CNP).

We have studied also weak localization (WL) and antilocalization (WAL) in graphene at

temperatures between 0.3 K and 15 K [4]. At low carrier density, we observed a transition

from WL to WAL driven by the increasing of the magnetic field while at high carrier density,

WAL was suppressed as a consequence of trigonal warping of the conical energy bands. We

analyzed the magnetic-field-driven WL-WAL transition, evaluating the relative strengths of

the various elastic-scattering mechanisms and estimating the decoherence lengths and rates

as a function of temperature, using an alternative method with respect to previously

reported studies.


26

References

[1] J. Martin et al., Nature Physics 5, 669 (2009)

[2] M. Amado, E. Diez, D. López-Romero, F. Rosella, J.M. Caridad, V. Bellani, D.K.

Maude. New Journal of Physics 12 053004 (2010).

[3] M. Amado, E. Diez, F. Rossella, V. Bellani, D. López-Romero and D. K Maude, J. Phys.:

Condens. Matter 24, 305302 (2012).

[4] S. Pezzini, C. Cobaleda, E. Diez, and V. Bellani, Phys. Rev. B 85, 165451 (2012)

Acknowledgments:

This work was supported partially by the projects: Ministerio de Ciencia e Innovación

(Spain): FIS2009-07880, and PCT420000-2010-08; Junta de Castilla y León (Spain):

SA049A10; Cariplo Foundation (Italy): QUANTDEV, and by EuroMagNET under the EU

contract n. 228043.



27

HIGH PULSED MAGNETIC FIELDS FOR NEUTRON DIFFRACTION

Fabienne DUC

Laboratoire National des Champs magnétiques Intenses, UPR3228 CNRS-INSA-UJF-UPS,

Toulouse & Grenoble, France

References:

[1] Y. Narumi et al., J. Synchrotron Radiat. 13, 271 (2006).

[2] P. Frings et al., Rev. Sci. Instrum. 77, 063903 (2006).

[3] Y. H. Matsuda et al., J. Phys. Soc. Jpn. 75, 024710 (2006).

[4] Y. H. Matsuda et al., J. Phys. Soc. Jpn. 76, 034702 (2007).

[5] O. Mathon et al., J. Synchrotron Radiat. 14, 409 (2007).

[6] C. Strohm et al., Phys. Rev. Lett. 104, 087601 (2010).

[7] S. Yoshii et al., Phys. Rev. Lett. 103, 077203 (2009).

[8] M. Matsuda et al., Phys. Rev. Lett. 104, 047201 (2010).

Acknowledgments:

Part of this research was funded by the ANR (Grant N°. ANR-10-BLN-0431/ MAGFINS).


Over the past years, there has been a growing interest in the use of high pulsed magnetic

fields (up to 40 T) at synchrotron and neutron facilities. Pulsed magnets are an economic

and flexible choice to generate high fields beyond the limits of current superconducting and

resistive magnet technology available in the laboratory. Because of the larger flux of

synchrotron x-ray sources compared to neutron facilities, the development efforts have been

first focused on synchrotron methods, such as powder diffraction [1-2], single crystal

diffraction [3], x-ray absorption spectroscopy [4], x-ray magnetic circular dichroism [5] and

nuclear forward scattering [6].

Neutron diffraction has complementary features to x-ray diffraction, and unique capabilities

for studying microscopically the magnetic properties of materials. Recently, a new

breakthrough has been made by combining a 30 T portable miniature pulsed magnet

designed by IMR/Sendai and a mobile capacitor bank developed by the LNCMI/Toulouse

with the world most intense neutron source of ILL. Successful experiments on frustrated

systems [7-8] with relatively high magnetic moments have already been carried out using

this experimental setup. Anyway, further developments have been undertaken to improve

the efficiency of the method and to pave the way for the investigations of materials bearing

small magnetic moments like, e.g., high Tc superconductors or quantum spin systems. These

results and new developments will be described here.


28

BRAGG-PEAK FOURIER TRANSFORM STM - A NEW

APPROACH TO IDENTIFYING ELECTRONIC BROKEN

SYMMETRY WITHIN THE CRYSTAL UNIT CELL

Inês A. FIRMO1,2, M.H. HAMIDIAN1,2, K. FUJITA1,2,3,

S. MUKHOPADHYAY1,2, J.W. ORENSTEIN4, H. EISAKI5,

S. UCHIDA3, M.J. LAWLER2, E.-A. KIM2 & J.C. DAVIS1,2,6,7

1CMPMS Department, Brookhaven National Laboratory, Upton, NY 11973, USA.

2Laboratory of Solid State Physics, Department of Physics, Cornell University, Ithaca, NY

14853, USA.

3Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.

4Department of Physics, University of California, Berkeley, CA 94720, USA.

5Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan.

6School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK.

7Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA.


Direct visualization of electronic-structure symmetry within each crystalline unit cell is a

new technique for complex electronic matter research. Several distinct types of such intra-

unit-cell (IUC) symmetry breaking can be studied through careful analysis of the real and

imaginary components of the Bragg peaks observed in Fourier transforms of electronic

structure images from spectroscopic imaging (SI)-STM data. However, establishing the

precise real-space symmetry point of each unit cell is crucial in defining the Fourier

transform phase for this powerful analysis. Exemplary of this challenge is the cuprate high-

Tc superconductor compound Bi2Sr2CaCu2O8+δ for which the Bi atoms in the surface BiO

layer are observable, while it is the invisible Cu atoms that define the relevant CuO2 unit-cell

symmetry point. We demonstrate, by imaging with picometer precision the electronic

impurity states at individual Zn atoms substituted at Cu sites, that the phase established

using the Bi lattice produces a ~2%(2) error relative to the Cu lattice. In this case, IUC

rotational symmetry breaking in the CuO2 plane can be determined reliably using the phase

assignment from the BiO layer [Hamidian, Firmo et al., New J. Phys. 14 053017 (2012)]. Using

this Bragg-peak Fourier transform STM technique, intra-unit-cell ‘nematicity’ (broken

rotational symmetry) has been observed in the electronic structure of the pseudo-gap phase

in several cuprate compounds [e.g. Lawler et al., Nature 466 347 (2010)]. We will discuss

other possible applications.


29

CIEMAT ACTIVITIES CONCERNING HIGH FIELD MAGNETS FOR

PARTICLE ACCELERATORS AND POWER APPLICATIONS

Luis GARCÍA-TABARÉS

CIEMAT, Madrid, Spain


More than 20 years ago CIEMAT started a group in Applied Superconductivity to develop

technologies related to High Field Magnets, particularly to those which are used in particle

accelerators. Since then, many developments have been carried out, not only in that field

but also in others like material characterization or power systems. This talk will describe

these developments as well as some related activities in which the group is now involved.


30

HIGH TEMPERATURE SUPERCONDUCTING MAGNETS:

FROM BULKS TO COILS

Xavier GRANADOS

ICMAB-CSIC, Barcelona, Spain


From early times of High Temperature Superconductivity (HTS) the expectancies of

increasing the working temperature o the classical superconducting magnets pushed to

develop the HTS counterpart. The peculiarities of the HTS materials, however, limited their

applicability to magnet manufacturing from a standard scope. Although this initial

limitations, alternatives that never were considered as the so called HTS Permanent

Magnets were opened achieving records of maximum flux density. Motors and other devices

were in the scope.

Nowadays, the state of the art of the HS materials allows facing the possible substitution of

the low temperature superconductors in coils manufacturing. A large and passionate way

should be covered but we can see some light at the end. The new high vacuum magnet

developed for the BOREAS beam line in ALBA synchrotron is a good example in which cost

and technical options have found equilibrium for achieving a successful design and

manufacturing.


31

THE UPPER CRITICAL FIELD OF A CUPRATE SUPERCONDUCTOR

Gaël GRISSONNANCHE

Université de Sherbrooke, Canada


The value of the upper critical field, Hc2, in cuprate superconductors is an open, interesting

question, subject to much debate. I will present our recent measurements of the thermal

conductivity in YBa2Cu3Oy performed in magnetic fields up to 35 T, from which we can

directly extract Hc2. The value of 24 T found at a doping p = 0.11 is remarkably low. I will

argue that Hc2 collapses in the underdoped regime because of the competing effect of a

phase with charge-density-wave order, also responsible for a reconstruction of the Fermi

surface.


32

MAGNETIC AND PSEUDOMAGNETIC FIELDS IN GRAPHENE

Paco GUINEA

ICMM-CSIC, Madrid, Spain


Graphene is a unique material, where signatures of the Integer Quantum Hall Effect are

observed at about 1 Tesla, or at room temperature. In addition, lattice strains simulate the

effect of orbital magnetic fields, making it possible to achieve effective fields in excess of

300T. A review of the properties of graphene under real and "synthetic" magnetic fields will

be given.


33

FRUSTRATED MAGNETISM AND SPIN TRANSITIONS VIA

LATTICE MAGNETO-STRAIN MEASUREMENTS IN PULSED

MAGNETIC FIELDS TO 100 TESLA

Marcelo JAIME

NHMFL, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.

References:

[1] M. Jaime, et al. PNAS 109, 12407 (2012).

[2] Y. Kohama et al., Phys. Rev. Lett. To be published

[3] M.M. Altarawneh et al., Phys. Rev. Lett. 109, 037201 (2012).


Strong geometrical frustration in magnets leads to exotic states, such as spin liquids, spin

supersolids and complex magnetic textures. SrCu2(BO3)2, a spin-1/2 Heisenberg

antiferromagnet in the archetypical Shastry-Sutherland lattice, exhibits a rich spectrum of

magnetization plateaus and stripe-like magnetic textures in applied fields. We reveal new

magnetic textures via optical FBG magnetostriction and magnetocaloric measurements in

fields up to 100.75 Tesla at 73.6 T and at 82 T which we attribute, using a controlled density

matrix renormalization group approach, to a new 2/5 plateau, and to the long-predicted 1/2-

saturation plateau. [1] BiCu2PO6 is a frustrated two-leg spin ladder compound with a spin

gap that can be closed with a magnetic field of approximately 20T. Magnetization,

magnetostriction and specific heat vs magnetic fields to 65 T were used to obtain the

anisotropic (H,T) phase diagram in single crystal samples for the first time. We propose that

the anisotropy and complex phase diagram result from the interplay between strong

geometrical frustration and spin orbit interaction. [2] Time permitting, we will also discuss

briefly the case of LaCoO3, where magnetic fields can be used to induce a series of spin

transitions at H > 60 T that have large effects in the lattice. The analogy with pressure–

induced spin transitions in Fe-containing magnesium silicate perovskites found in Earth’s

mantle make large magnetic fields a unique study technique. [3] Work at the NHMFL was

supported by the National Science Foundation, the US Department of Energy trough the

BES “Science at 100T” program, and the State of Florida.


34

SOLITON LATTICE PHASE OF SPIN-PEIERLS STATE

I. HEINMAA, Enno JOON & R. STERN

National Institute of Chemical Physics and Biophysics Akadeemia tee 23,

Tallinn 12618, Estonia


One-dimensional magnetic spin ½ chains undergo spin-Peierls (SP) transition caused by

crystal lattice dimerization at low temperatures. The dimerization or doubling of a unit cell

is a result of spin-phonon magnetoelastic coupling and takes place in CuGeO3 at TSP= 14K.

However, this state is unstable against the high magnetic field H>Hc=12.5T, which creates

domain walls inside the dimerized phase. This soliton lattice phase exists between lower and

higher TSP in other spin-Peierls compounds too: TiClO (65K/95K) and TiBrO (27K/48K), but

it isn’t caused by magnetic field. For establishing the cause of soliton lattice phase we have

investigated the spin-Peierls compound TiPO4 with highest TSP=112K (73K/112K) by 31P and 47,49Ti NMR in high magnetic field 8.5 and 14.1 Tesla. In paramagnetic phase T> TSP the

Knight shift follows susceptibility and at T<73K the NMR line splits indicating dimerization.

In temperature interval 73K<T<112K inhomogeneous distribution of magnetization is clearly

seen demonstrating spin paired and normal phase coexisting. Additional measurements and

comparing with the data of the compounds mentioned above allowed us conclude that the

soliton lattice phase in these crystals is caused by inter-chain spin-spin interaction.


35

SUPERCONDUCTING MAGNETS AND CRYOGENICS

FOR THE LARGE HADRON COLLIDER (LHC)

Philippe LEBRUN

CERN, Geneva (Switzerland)


Guiding and focusing the very rigid beams of 7 TeV protons around the 26.7 km quasi-

circular tunnel of the LHC requires several thousand high-field superconducting magnets

operating in superfluid helium at 1.9 K. The main magnets – 1232 twin-aperture dipoles and

400 twin-aperture quadrupoles – are made of two-layer cos coils wound from some 7500

km of Nb-Ti «Rutherford» cable with tightly toleranced mechanical, electrical and magnetic

characteristics, to produce a field of 8.33 T and a gradient of 223 T/m, respectively, in a 56

mm diameter bore. Powered in eight independent 3.3 km long sectors by currents of up to 12

kA, the magnets store inductively a large energy (11 GJ in total) which must be released in a

controlled manner upon resistive transitions, either natural or provoked by beam losses. All

high-current magnet circuits (the sum of which amounts to 3.4 MA) are powered through

current leads using high-temperature superconductors, in order to limit the cryogenic load.

In order to reach the high magnetic fields with the limited performance of Nb-Ti, the

magnets operate well below the normal boiling point of helium (4.2 K), in pressurized

superfluid helium at 1.9 K. In addition to lower temperature, superfluidity allows to take

advantage of the excellent transport properties of helium II to stabilize the conductor

against thermal disturbances and extract heat from the windings, provided the insulation

system allows sufficient permeation and percolation paths. The thermodynamic penalty of

operating at low temperature imposes tight control of the heat loads, e.g. by thermal

shielding and interception at higher temperature, as well as high efficiency of the

refrigeration and cryogenic distribution systems. We present the technical rationale of the

system and report on its recent operation.


36

PROGRESS OF THE PULSED HIGH MAGNETIC FIELD FACILITY

AT WUHAN NATIONAL HIGH MAGNETIC FIELD CENTER

Liang LI

Wuhan National High Magnetic Field Center, Wuhan, China


Since April 2008 the Pulsed High Magnetic Field facility funded by the Chinese National

Development and Reformation Committee has been under development at the Wuhan

National High Magnetic Field Center at Huazhong University of Science and Technology

(HUST). Magnets with bore sizes from 12 to 34 mm and the peak fields up to 83 tesla have

been developed and are in operation. The power supplies for these magnets are a capacitor

bank with 13 modules of 1MJ/25 kV each, a 100 MVA/100 MJ flywheel pulse generator and a

100 kAh battery bank. The objective of the facility is to accommodate external users for

extensive experiments in pulsed high magnetic fields. 8 measurement stations including

transport, magnetization, magneto-optics, Electron Spin Resonance (ESR), NMR and so on

have been developed and are operational at temperatures in the range from 50 mK to 400 K.

Experiments have been carried out with extensive materials such as HTS, topologic

insulators, semiconductors, molecular magnets and so on. Quantum oscillations and phase

transitions have been observed in both the transport and the magnetization measurements.

Magneto-optic Kerr Effect (MOKE), Faraday Rotations, magneto-optical

photoluminescence, magneto-optical absorption and reflection have been measured at the

magneto-optics measurement station. The designing and the construction of the facility and

the experimental results from each measurement station are presented.


37

HIGH FIELD MAGNET LABORATORY (HFML) NIJMEGEN

Jan Kees MAAN

Radboud University Nijmegen, High Field Magnet Laboratory

Faculty of Science, postvak 22,P.O. box 9010

6500 GL Nijmegen, The Netherlands

THE EUROPEAN MAGNETIC FIELD LABORATORY (EMFL)


The High Field Magnet Laboratory at the Radboud University of Nijmegen is dedicated to

generate the highest possible continuous magnetic fields, use them for its own research and

make them available to external users. At present the laboratory has several DC magnets

with maximum fields up to 33T. A new 38T DC magnet is being installed and a 45T hybrid

magnet is under development. With the magnets a wide variety of experiments can be

performed ranging from thermodynamic properties like specific heat, magnetization,

thermoelectric power and magneto transport to optical spectroscopy in the far infrared (spin

resonances, magneto plasma effects, etc.) and in the visible (Raman, luminescence,

reflection, transmission, Kerr, Cotton Mouton effect, etc.). The DC fields are generated with

a 20MW 4ppm stability power supply and the dissipated energy is cooled with a water and

cooling installation. Special care is taken to reduce electrical and mechanical noise in the

magnets to allow single probe experiments like confocal optics and scanning probe

techniques that are presently developed. HFML receives about 100 external guest

researchers every your working on 45 different research project that have passed a peer

reviewed external selection panel. The local research program is on soft matter,

semiconductors and nanostructures and correlated electron systems.

The EMFL is a formalized collaboration between the Laboratoire National des Champs

Magnétiques Intenses (LNCMI) in Grenoble (static field) and Toulouse (pulsed field) of the

Centre National de la Recherche Scientifique (CNRS, France); the Hochfeld-Magnetlabor

Dresden (HLD) of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR, Germany) and the

High Field Magnet Laboratory Nijmegen (HFML, Radboud University Nijmegen/Stichting

Fundamenteel Onderzoek der Materie, the Netherlands). The EMFL offers access to the

magnetic fields and experimental facilities at the installations through an external selection

panel. EMFL will coordinate the work of the three partners, organize network activities like

workshops and schools and will represent EMFL externally. Formally EMFL will be legal

entity in the form of a foundation that is directed by the three directors of the partner

laboratories and governed by a council in which all members participate. EMFL can agree

contracts with new partners. These new members should contribute to the running costs of

the laboratories and will receive privileged access to the installations and full support and

expertise of the laboratories that make up the EMFL infrastructure.


38

NEXT GENERATION OF HIGH FIELD

SUPERCONDUCTING MAGNETS

Ziad MELHEM

Oxford Instruments, Tubney Woods, Abingdon, OX13 5QX, UK


High filed magnets using low temperature superconductors (LTS) has hit the limit of

performance of these materials. Users need for superconducting magnet greater than 23T for

physical sciences, NMR or ICR applications will require new innovation in superconducting

magnet engineering. The talk presents an overview of high fields for research and industry.

In particular the emphasis is on high field superconducting technology and the dependence

of high fields on the development of superconducting materials. The production of high

magnetic fields using low temperature superconductors (LTS) has become common place.

However, the large magnet sizes and their associated high cooling costs have often

precluded the full utilization of these research capabilities. Recent advances in internal Sn

superconductors and Cryofree technology together with advances in high temperature

superconductors (HTS) have opened up a new era in superconducting magnet development.

A new generation of superconducting magnets is undergoing development and exploits the

current performance of HTS and LTS materials together with innovative solutions in

engineering the integration of coils from different materials and manages the impact of

increased stored energy on quench management and coil structure integrity.


39

BEYOND 100 TESLA: SCIENTIFIC EXPERIMENTS

USING SINGLE-TURN COILS

Oliver PORTUGALL

Laboratoire National des Champs Magnetiques Intenses, Toulouse, France


On a sufficiently short timescale, the mechanical inertia of a magnet can impede its

deformation by an applied magnetic field more efficiently than any reinforcement structure.

The latter fact has given rise to a separate category of field generation techniques. These so-

called Megagauss or destructive pulsed techniques represent the only option for generating

fields well above 100 T in a macroscopic volume.

The intrinsically short duration of Megagauss fields -- typically a few microseconds --

represents a formidable challenge for implementing scientific experiments. The advent of

fast electronics and opto-electronics has nevertheless rendered Megagauss fields

increasingly accessible for applications in areas such as solid state spectroscopy.

Since 2009 the LNCMI hosts one out of three Megagauss generators worldwide that make

use of capacitor-driven single-turn coils to perform scientific experiments in fields up to 200

T. In this presentation we discuss recent optical measurements on Graphite and Graphene

in order to practically demonstrate the scientific potential of our installation.


40

THE LABORATOIRE NATIONAL DES CHAMPS

MAGNÉTIQUES INTENSES

Geert RIKKEN

Laboratoire National des Champs Magnetiques Intenses, Grenoble, France


The Laboratoire National des Champs Magnétiques Intenses (LNCMI) is Europe’s largest

research facility for the generation and scientific use of high magnetic fields, both DC

(Grenoble) and pulsed (Toulouse). It is operated by the French Centre National de la

Recherche Scientifique for the benefit of all French and European high field users.

In this presentation I will describe the current and future technical and scientific activities at

the LNCMI.


41

DEVELOPMENTS AT PULSED HIGH FIELD LABORATORY IN ISSP

Masashi TOKUNAGA

International MegaGauss Science Laboratory, The Institute for Solid State Physics,

The University of Tokyo


In high field laboratory at ISSP (The Institute for Solid State Physics), we are developing

non-destructive and destructive pulse magnets and measuring basic physical properties in

various kinds of magnetic materials, semiconductors, and superconductors in high magnetic

fields. Destructive magnets provide unique opportunity for the experiments over 100T. The

electro-magnetic flux compression system can generates the field up to 730 T, which is the

highest field generated by the indoor facility. The single-turn coil system can generate the

fields up to 200 T in rather convenient manner. With using these systems, we performed

optical measurements on semiconductors and frustrated magnets. Non-destructive magnets

were wound using newly developed high-strength Cu-Ag wires. Our new generation

magnets can generate the fields over 85 T in a monocoil style driven by a single capacitor

bank. Some of the non-destructive magnets are activated by the flywheel generator that has

the world highest power as a DC generator. The latest developments in the field generation

will be introduced together with some scientific achievements using these magnets.


42

PROPAGATION OF MAGNETIC AVALANCHES AND

EMITTED ELECTROMAGNETIC RADIATION IN Mn12-AC

UNDER HIGH FIELD SWEEP RATES

Johan VANACKEN1, W. DECELLE1, V. V. MOSHCHALKOV1,

J. SURYANARAYANA2, S. VÉLEZ3 & J. TEJADA3

1Institute for Nanoscale Physics and Chemistry, Celestijnenlaan 200D, B-3001 Leuven, BE

2Department of Physics, Indian Institute of Technology Hyderabad, Yeddumailaram, Hyderabad –

502205, IN

3Grup de Magnetisme, Facultat de Física, UBX, Martí i Franquès 1 4a planta, 08028 Barcelona, ES

References:

[1] Physical Review Letters 102 (2009) 027203.


Time-resolved measurements of the magnetization reversal in single crystals of Mn12Ac in

pulsed magnetic fields, at magnetic field sweep rates from 1.5 kT/s up to 7 kT/s, suggest a

new process that cannot be scaled onto a deflagration-like propagation driven by heat

diffusion. The sweep rate dependence of the propagation velocity, increasing from a few 100

m/s up to the speed of sound in Mn12Ac, indicates the existence of two new regimes at the

highest sweep rates, with a transition around 4 kT/s, that can be understood as a magnetic

deflagration-to-detonation transition [1].

Under the same high field sweeping rates, the emission of heat and electromagnetic

radiation (EMR) from a Mn12-Ac crystal have been tested by using RuO2 thermometers

capable to detect EMR by the molecular magnets. We have performed an experiment based

on the use of two matched compensating RuO2 thermometers, of which one is carrying the

Mn12-Ac crystal. Two field pulses of the same field polarity were generated, and as such the

second pulse could be used as a background subtraction. In the second shot of the same

field polarity, immediately after 1st shot, there is no response corresponding to the emission

of the sample. This confirms that the signal that is observed in the first shot is due to the

sample reversing its magnetization and it exhibits two peaks. Concerning the 1st fast peak,

as it is observed just at the 3rd resonance, this could be due to fast emission of EMR, i.e.

superradiance. As for the second and broad peak concerns, this is attributed to the sample

self-heating (via phonons) after the avalanche process because of the large time-scale.


43

REENTRANT SUPERCONDUCTIVITY IN NANOPATTERNED SYSTEMS

R. CÓRDOBA1,2, T. I. BATURINA3,4, J. SESÉ1,2, A. YU. MIRONOV3,

J. M. DE TERESA5,2, M. R. IBARRA1,5,2, D. A. NASIMOV3, A. K. GUTAKOVSKII3,

A. V. LATYSHEV3, I. GUILLAMÓN6, H. SUDEROW6, S.VIEIRA6,

M. R. BAKLANOV7, YU. M. GALPERIN8,9, N. B. KOPNIN10, A. S. MELNIKOV11,

J. J. PALACIOS12, D. VODOLAZOV11, & Valerii M. VINOKUR4

1Instituto de Nanociencia de Aragón, Universidad de Zaragoza, Zaragoza, 50018, Spain

2Departamento de Fısica de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza

3A.V. Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentjev Avenue, Novosibirsk,

630090 Russia

4Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA

5Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, Facultad de Ciencias,

Zaragoza, 50009, Spain

6Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto

de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid, Spain

7IMEC Kapeldreef 75, B-3001 Leuven, Belgium

8Department of Physics, University of Oslo, PO Box 1048 Blindern, 0316 Oslo, Norway

9Centre for Advanced Study, Drammensveien 78, Oslo, Norway 0271, Oslo, Norway

10Low Temperature Laboratory, Aalto University, P.O. Box 13500, FI-00076 AALTO, Finland

11Institute for Physics of Microstructures, Russian Academy of Sciences, 603950, Nyzhny Novgorod,

GSP-105, Russia


Under the applied current magnetic vortices move and dissipate the energy driving a

superconductor into a resistive state. We demonstrate experimentally and theoretically that

confining vortices within the narrow superconducting constrictions with the characteristic

dimensions comparable to the size of the vortex core, one can reverse the detrimental effect

of the magnetic field and recover superconductivity. We investigate two different exemplary

systems, the superconducting wire and the thin superconducting film patterned into a

regular array of nanoholes, and observe the drop of the resistance by several orders of

magnitude to immeasurably small in a wide range of magnetic fields and temperatures. We

show that the mechanism behind the magnetic field-induced superconductivity is the

combined action of merging of the densely packed constricted Abrikosov vortices into large

immobile hypervortices and the effects of surface superconductivity. We develop a

quantitative theory of reentrant superconductivity in superconducting strips in terms of the

phase-slip concept and show that the experimentally observed non-monotonic phase slips

related magnetoresistance results from the existence of the longitudinal order parameter

instability near the transition between the vortex-free and vortex states in a

superconducting strip. We propose a quantitative description of the resistance of the wires

and films and demonstrate that theoretical results favorably compare with the experiment.


44

SYMMETRY BREAKING EXCITATIONS IN IRON-

CHALCOGENIDE SUPERCONDUCTORS

Peter WAHL

Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany and SUPA,

School of Physics & Astronomy, University of St. Andrews, UK


The emergence of nematic electronic excitations is a recurring theme in many correlated

electron materials. In recent years, in a number of parent compounds of the iron-based

superconductors evidence for C2 symmetric electronic states has been found from STM,

transport, ARPES and other techniques. Although the symmetry breaking is usually stronger

than expected, the underlying crystal structures of most iron-based superconductors have a

tendency towards orthorhombic distortion – C4 symmetry is already broken in the lattice

structure.

Here I present data obtained by spectroscopic imaging STM of a iron chalcogenides

superconductor with a Tc of 14K. We observe significant spatial inhomogeneity of the

superconducting gap. Moreover, our data show the existence of symmetry breaking

electronic excitations in a crystal which does not show a structural phase transition. The

symmetry breaking excitations persists above Tc into the normal state. I discuss possible

origins of these anisotropic excitations by relating them to tight-binding calculations as well

as implications for superconductivity in iron-based materials and some of the proposed

mechanisms.


45

RESEARCH AND INFRASTRUCTURE AT THE DRESDEN

HIGH MAGNETIC FIELD LABORATORY

Jochen WOSNITZA

Hochfeld-Magnetlabor Dresden (HLD), Helmholtz-Zentrum Dresden-Rossendorf,

D-01314 Dresden, Germany; [email protected]/hld


In this talk, a brief overview on the experimental infrastructure and the in-house research of

the Dresden High Magnetic Field Laboratory (Hochfeld-Magnetlabor Dresden, HLD) will be

given. High magnetic fields are one of the most powerful tools available to scientists for the

study, modification, and control of the state of matter. The application of magnetic fields,

therefore, has become a commonly used instrument in condensed-matter physics and the

demand for the highest possible magnetic-field strengths increases continuously. At the

HLD, that in 2007 has opened its doors for external users, pulsed magnetic fields beyond 90

T have been reached. The laboratory recently has achieved a record field of 94.2 T having

the ambitious goal of reaching 100 T on a 10 ms timescale. In the pulsed fields, numerous

experimental methods are available allowing to measure e.g. electrical transport,

magnetization, magnetostriction, ultrasound, ESR, and even NMR with very high resolution.

As a unique feature, a free-electron-laser facility next door allows high-brilliance radiation to

be fed into the pulsed-field cells of the HLD, thus making possible high-field magneto-

optical experiments in the range 3-250 µm. In-house research of the HLD focuses on

electronic properties of strongly correlated materials at high magnetic fields. This includes

the investigation of novel magnetic materials, the determination of the doping-dependent

evolution of the Fermi surface of electron-doped high-temperature superconductors by

means of Shubnikov de Haas measurements as well as the recently found evidence for the

existence of the Fulde Ferrell Larkin Ovchinnikov state in an organic superconductor.


46

SCANNING TUNNELING SPECTROSCOPY OF VORTEX CORE STATES

IN HIGH-TC SUPERCONDUCTOR Bi2Sr2CaCu2Ox

Shunsuke YOSHIZAWA1, T. KOSEKI1, K. MATSUBA1,

T. MOCHIKU2, K. HIRATA2, & N. NISHIDA1

1Department of Physics, Tokyo Institute of Technology

2Superconducting Materials Center, National Institute for Materials Science


In the vortex core of high-Tc cuprate superconductor Bi2Sr2CaCu2Ox (Bi2212), the local

density of states has been found to exhibit spatial modulation in the two Cu-O bond

directions with a period of 4a0 (a0 is the Cu-O-Cu bond length). Our previous study showed

that the spatial modulation of electron-like states and that of hole-like states are in anti-

phase and that the two Cu-O bond directions are non-equivalent in the vortex core.

However, the nature of the vortex core states is still unclear.

We performed scanning tunneling spectroscopy of slightly-overdoped Bi2212 at 4.2 K in a

high magnetic field of 14.5 T. We have measured the vortex core states and the

inhomogeneity of electronic states simultaneously with a spatial resolution of 47 pm. A

possible interpretation of the vortex core states will be discussed.


47

Abstracts of Posters

Abstracts of Posters


48

MAGNETOELASTIC COUPLING IN STRAINED

La0.7Ca0.3MnO3//BaTiO3 THIN FILMS

Aurora ALBERCA1,4, C. MUNUERA1,4, N. M. NEMES2,4,

F.J. MOMPEAN1,4, J. TORNOS2,4, C. LEON2,4, A. DE ANDRÉS1, T. FEHÉR3,

F. SIMON3,J. SANTAMARIA2,4 & M. GARCIA-HERNANDEZ1,4

1Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones

Científicas, Sor Juana Inés de la Cruz, 3, ES-28049 Madrid (Spain)

2Departamento de Física Aplicada III, Universidad Complutense, Ciudad Universitaria, ES-

28040 Madrid (Spain)

3Budapest University of Tecnology and Economics, Institute of Physics, Department of

Experimental Physics, H 1521 Budapest (Hungary)

4Laboratorio de Heteroestructuras con aplicación en Spintronica, Unidad Asociada

CSIC/Universidad Complutense Madrid, Sor Juana Inés de la Cruz, 3, ES-28049 Madrid, Spain

Multiferroic heterostructures combining ferroelectrics and ferromagnets are being studied

in order to design systems with artificial magnetoelectric effect. Potential applications in

magnetoelectric devices (as feasible alternatives to MRAM and FRAM, for example) make

them of vital importance in spintronics (Refs [1] and [2]). In our systems, we used BaTiO3 as

a ferroelectric substrate and La0.7Ca0.3MnO3 manganite, well known for its strengthened

tendency towards electronic phase separation, in order to enhance the effects of

inhomogeneous strain maps on these substrates.

La0.7Ca0.3MnO3 ultra-thin films (10nm) epitaxially grown on BaTiO3 substrates exhibit

anomalous magnetic and transport properties: magnetic loops showing Matteucci-like

shapes, high electroresistance, and a second metal insulator transition have been observed

in the temperature interval 80K-160K, below its Curie temperature (Refs [5] and [6]). XRD

studies in the rhombohedric (T<180-190K), orthorhombic (180-190K<T <270-280K),

tetragonal (270-280K<T<293K) and cubic (T>293K) BaTiO3 phases, show the complex strain

map and the structure evolution of the thin film. As it has been seen in Refs [5] and [6], a

possible explanation for these properties can be found in the substrate polarization,

corrugation and/or strain (Refs [3] and [4]), and in the La0.7Ca0.3MnO3 tendency to phase

separation.

Here, we explore the role of corrugation and large internal strains in magnetic anisotropy

energy in La0.7Ca0.3MnO3//BaTiO3 samples. First, anisotropy constants are obtained with

simulations of Ferromagnetic Resonance data, showing significant differences between our

La0.7Ca0.3MnO3//BaTiO3 samples and La0.7Ca0.3MnO3 10nm thin films grown on non-

ferroelectric SrTiO3 substrates, where corrugation is inexistent. Then, Polarized Neutron

Reflectometry experimental results are addressed as two layers in the magnetic distribution

profile. These results are then studied in terms of magnetoelastic coupling. Strains of 1-10%

in thin films require an extended analysis of the magnetoelastic contributions to the free

energy. The power series expansion of the free energy may include terms of the second order


49

References:

[1] D. Khomskii, Physics 2, 20 (2009).

[2] M. Bibes, J. E. Villegas, and A. Barthélémy, Adv. Phys. 60, 5 (2011).

[3] J. D. Burton and E. Y. Tsymbal, Phys. Rev. B 80, 174406 (2009).

[4] S. Dong, X. Zhang, R. Yu, J. M. Liu, and E. Dagotto, Phys. Rev. B 84, 155117 (2011).

[5] A. Alberca et al., Phys. Rev. B 84, 134402 (2011)

[6] A. Alberca et al., Phys. Rev. B, (2012)

[7] R.C. O‘Handley and S.-W. Sun, J Magn. Magn. Mater., 104, p. 1717-1720.


in strains (Ref. [7]). In our thin films, substrate corrugation near the surface is responsible of

huge local strains that affect La0.7Ca0.3MnO3 properties, as described in second paragraph.

The stress decreases far from the interface through relaxation, and in the case of thicker

layers the effect is diminished. The differences in the anisotropic constants are studied and,

the out of plane spin population postulated in Ref [3] as an explanation for the Matteucci-

like shaped magnetic loops confirmed.



50

MODIFIED COLLAGEN WITH MAGNETIC FUNCTIONALITY

Julian DAICH1 & M. VÉLEZ1,2

1INC Universidad Autónoma de Madrid, IMDEA Nanociencias

2CP-CSIC - Grupo de Biocatálisis, Instituo de Catálisis y Petroquímica, CSIC

Introduction. Most biological matter is diamagnetic in nature having negative magnetic

susceptibility. Magnetic nanoparticles ( MP) are a class of nanoparticle which can be

manipulated or oriented using magnetic fields. Such particles commonly consist of a

magnetic elements such as iron, nickel or cobalt and their chemical derivatives. During

magnetic resonance imaging( MRI) procedures water molecules in the proximity of MP

attached to a protein will have relaxation times different from that of the water molecules

around the protein itself. Such differences in relaxation times, also called contrast, are a

function of the size and shape of MP. We propose to prepare magnetically functionalized

substrates designed to be used as probes for reporting specific enzymatic activity. Such

magnetically functionalized substrates are prepared by docking MP over substrates of

macromolecular sizes. These substrates must be significantly bigger than the size of a MP.

Thus when magnetically functionalized substrates are digested by an enzyme, the MP tend

to aggregate( figure A). The effect of MP on MRI contrast is different when MP are

anchored in dispersed form over a substrate compared to MP aggregated. We started

working with a collagen model of the method. Collagen is the most abundant protein of

connective tissue and is the substrate of collagenases, enzymes which are part of a broader

family called matrix metalloproteinases( MMP) that are involved tissue regeneration.

Materials and Methods. A protocols to attach MP particles on collagen fibrils was developed

by means of first mixing on acetonitrile APTES; DIEA with glutaric anhydride for 24 h in a

dry atmosphere, separately homogenizing and suspending collagen fibrils in acetonitrile,

mixing both mixtures with DIPCD for 48h, replacing the acetonitrile with ethanol by

evaporation, adding magnetite nanoparticles, mixing for 48 hs, replacing the ethanol with

water by evaporation, setting the resulting suspension at pH3, mixing for 72 h at 4ºC,

separating the excesses by ultracentrifugation and liofilizing. MRI studies at 4.7 T to

determinate the effect of collagenase and controls over 4mg of magnetically functionalized

collagen immobilized in 1 ml of agarose with CaCl2 were conduced. Circular dichroim

spectra of modified collagen fibrils with and without collagenase exposition were also

studied.

Results and Discussion. These studies showed a reduced T2 mean of a 10 +/-2% for

magnetically functionalized collagen exposed to collagenase compared to being exposed to a

saline control. Circular dichroism spectra showed no signs that modified collagen tertiary

structure was altered and that it is affected by collagenolytic activity.


51


Conclusions. We developed a novel and promising technique to assess enzymatic activity

with potential applications in vivo. We are currently working on improving protocols for

magnetic labeling, extending the substrates to other biomarkes and determining viable

delivery methods for clinical use.


52

LOW TEMPERATURE MAGNETIC TRANSITIONS

IN SINGLE CRYSTALLINE HoBi

Antón FENTE1, M. GARCÍA-HERNÁNDEZ2, N. M. NEMES2, P.C. CANFIELD3, S. VIEIRA1 & H. SUDEROW1

1Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia

Condensada Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias Universidad Autónoma de Madrid, E-28049 Madrid, Spain

2Instituto de Ciencia de Materiales de Madrid, CSIC, Es-28049 Madrid, Spain

3Ames Laboratory and Department of Physics and Astronomy, Iowa State University,

Ames, Iowa 50011, USA


We present resistivity and magnetization measurements in high quality single crystals of

HoBi, with a residual resistivity ratio of 126. We find, from the temperature and field

dependence of the magnetization, an antiferromagnetic transition at 5.73 K, which evolves,

under magnetic fields, into a series of up to five metamagnetic phases.



53

NATURE OF THE MAGNETIC COUPLING IN Co/MnF2 BILAYERS:

COMBINED STUDIES

José Luis F. CUÑADO1,2, C. RODRIGO2,3, P. PERNA2,3, A. BOLLERO2,3,

F.TERÁN1,2,3, N. S. SOKOLOV4, S. GASTEV4, S. SUTURI4, A. BANSHIKOF4,

V. FEDOROV4, D.BARANOV4, K. KOSHMAK4, L. PASQUALI6,

J. NOGUÉS5, J. CAMARERO1,2,3 & R. MIRANDA1,2,3

1Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid,

28049 Madrid, Spain.

2Instituto "Nicolas Cabrera", Universidad Autónoma de Madrid, 28049 Madrid, Spain

3Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia),

Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain.

4Ioffe Physical-Technical Institute Division of Solid State Physics.

5Institut Catala de Nanotecnologia, Spain Campus Universitat Autonoma de Barcelona.

6University of Modena, Italy Department of Materials Engineering.


We present a detailed study of temperature dependence of magnetization reversal

properties in artificial magnetic nanostructures, by using a new experimental set-up that

allows us to measure simultaneously magneto-resistance and vectorial-Kerr hysteresis loops

at full angular range of the applied field angle, and in a broad temperature range (4 K to 500

K). Co/MnF2 bilayers have been studied using this device.

New exchange bias phenomena at room temperature have been found, in particular, field-

induced exchange bias above the MnF2 Neel temperature.

Comparison with element-sensitive XCMD measurements is made to confirm the observed

exchange bias behavior.


54

ESR AND BANDSTRUCTURE IN NbFe2

Tobias FÖRSTER1, J. SICHELSCHMIDT2, M. BRANDO2,

D. GRÜNER2 & F. STEGLICH2

1Dresden High Magnetic Field Laboratory

2MPI for Chemical Physics of Solids Dresden


The Laves phase compound NbFe2 belongs to the small group of low temperature itinerant

magnets. It possesses a magnetically ordered ground state which is believed to be of spin-

density-wave type.

Furthermore, signatures of a logarithmic Fermi-liquid breakdown suggest the existence of a

quantum critical point on the Nb-rich side of the phase diagram. A largely enhanced Stoner

factor indicates the presence of FM correlations, which, in general, support the observability

of a conduction electron spin resonance (ESR).

We present our results of ESR measurements on polycrystalline samples of NbFe2. The ESR

data is analyzed in terms of a conduction ESR being subject to strong exchange

enhancements. The unexpected behavior of the ESR linewidth made it necessary to get a

detailed understanding of the band structure. Therefore we also present DFT calculations

that address this behavior.


55

SCANNING TUNNELING MICROSCOPY IN

SUPERCONDUCTING LAYERS OF 2H-TaSe2

José Augusto GALVIS1, P. RODIÈRE2, I. GUILLAMÓN1,3, M.R. OSORIO1,

J.G. RODRIGO1, L. CARIO4, E. NAVARRO-MORATALLA5,

E. CORONADO5, S. VIEIRA1 & H. SUDEROW1

1Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias Universidad Autónoma de Madrid, E-

28049 Madrid, Spain

2Institut Néel, CRS/UJF, 25, Av. des Martyrs, BP166, 38042 Grenoble Cedex 9, France

3H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK

4Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssiniére, BP

32229, 44322 Nantes Cedex 03, France

5Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Catedrático José Beltrán 2, 46980

Paterna, Spain


We present scanning tunneling spectroscopy measurements at 150 mK in single layer

crystals of 2H-TaSe2. We find a singular spatial dependence of the tunneling conductance,

changing from a zero bias peak on top of Se atoms to a gap in between Se atoms. The zero

bias peak is additionally modulated by the commensurate 3a0 × 3a0 charge density wave of

2H-TaSe2. Multilayers of 2H-TaSe2 show, by contrast, a homogeneous superconducting gap

with a critical temperature of about 1K. The zero bias peak in single layers of 2H-TaSe2

evidences a zero energy bound state. We discuss possible origins for such a peculiar

electronic spectrum, which seems to be characteristic of small superconducting single layers

of 2H-TaSe2.



56

INFLUENCES OF Ni-DOPING ON CRITICAL BEHAVIORS OF

La0.7Sr0.3Mn1-xNixO3

Dianta GINTING, D. NANTO, Y. D. ZHANG, S. C. YU & T. L. PHAN

Department of Physics, Chungbuk National University, Cheongju, South Korea


We have studied the critical behaviors of rhombohedral La0.7Sr0.3Mn1-xNixO3 (x = 0.01-0.03)

manganites by analyzing isothermal magnetization data recorded at temperatures around

the ferromagnetic-paramagnetic phase transition (the Curie temperature, TC). The

experimental results reveal that all the samples undergo a second-order magnetic phase

transition. Using the modified Arrott plot method, the critical parameters obtained are TC =

357.3 K, β = 0.394, γ = 1.092 and δ = 3.99 for x = 0.01; and TC = 352.6 K, β = 0.400, γ = 1.018,

and δ = 3.79 for x = 0.02; and TC = 342.7 K, β = 0.468, γ = 1.010, and δ = 2.67 for x = 0.03. With

these critical exponents, the isothermal magnetization data around TC fall into two branches

of a universal function M(H, ε) = |ε|βf±(H/|ε|β+γ), where ε = (T-TC)/TC is the reduced

temperature. This proves that the critical parameters determined are reliable, and in good

accordance with the scaling hypothesis. In our case, the β values for x = 0.01 and 0.02 are

close to those expected for the 3D Heisenberg model with ferromagnetic short-range

interactions, while the β value for x = 0.03 is close to that expected for the mean-field theory

with ferromagnetic long-range interactions. It means that the increase of Ni-doping

concentration in La0.7Sr0.3Mn1-xNixO3 can lead to ferromagnetic long-range order.


57

MECHANICAL BEHAVIOR OF 2G HTS COATED

CONDUCTORS OF YBCO AT 300 AND 77 K

Konstantina KONSTANTOPOULOU1, X. GRANADOS2,

J. Y. PASTOR1, X. OBRADORS2

1Departamento de Ciencia de Materiales, E. T. S. I de Caminos, Canales y Puertos, Universidad

Politécnica de Madrid, c/Profesor Aranguren s/n, 28040, Madrid, Spain

2ICMAB-CSIC, Campus Universidad Autónoma de Barcelona, 0893, Cerdanyola del Vallès,

Barcelona, Spain


HTS coated conductors have been widely studied to achieve long length as well as high

critical current. It has been demonstrated that during the fabrication process as well during

their operation as a magnet, the superconductors are called to withstand mechano-

electromagnetic strains. Therefore, the study of their mechanical properties during the

service conditions is critical for their functional use.

The present work studies the mechanical behavior of commercial 2G HTS coated conductors

based on YBCO at room temperature and at service temperature, 77 K.

The mechanical properties of this material have been studied by tensile strength test.

Additionally, it has been investigated the strain effect on the critical current, Ic. During the

tests, Digital Image Correlation (DIC) has been applied to obtain the complete strain

contour plots developed on the specimen surface. Moreover, mechanical fatigue tests up to

failure have been carried out to study the durability of the material.

Finally, has been studied the fracture surface of the tested tapes in order to investigate the

delamination process and the parameters that control the fracture of the material.


58

ELECTRONIC PHASE SEPARATION CLOSE TO THE

SUPERCONDUCTOR TO INSULATOR TRANSITION IN

ULTRA THIN TiN FILMS

Prasanna D. KULKARNI1, H. SUDEROW1, S. VIEIRA1,

T. BATURINA2,3 & V. VINOKUR3

1Laboratorio de Bajas Temperaturas. Departamento de Física de la Materia Condensada. Instituto de Ciencia de Materiales Nicolás Cabrera. Facultad de Ciencias. Universidad

Autónoma de Madrid, 28049 Madrid, Spain.

2A.V. Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentjev Avenue,

Novosibirsk, 630090 Russia

3Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA


We present scanning tunneling microscopy experiments at 100 mK and under magnetic

fields in ultra thin superconducting polycrystalline TiN films close to the superconductor to

insulator transition. Using large scale tunneling conductance maps, we find sizable

inhomogeneities with insulating-like regions comprising many small crystallites, separated

from superconducting regions. When increasing the magnetic field, we observe that the

conductance maps become homogeneous, losing signatures of phase separation around 4 T.



59

THE ÈVEN’ AND ÒDD’ MAGNETIC EXCITATIONS IN YBa2Cu3O6.9

Christopher LESTER1, S. M. HAYDEN1, J. KULDA2,

N. HARI BABU3 & D. A. CARDWELL3

1HH Wills Physics Laboratory, Bristol, UK

2Institut Laue-Langevin, Grenoble, France

3Engineering Department, University of Cambridge, UK


It has been well known for some time that on cooling through Tc, the spin excitation spectra

of cuprate superconductors becomes dominated by the neutron spin resonance, a collective

mode centred at QAF. We have used polarised inelastic neutron scattering to measure the

magnetic excitations of YBa2Cu3O6.9, unequivocally confirming the magnetic character of the

neutron spin resonance in both the odd and even channels. We find that the resonance in

the odd channel is anisotropic in spin space, that is the out of plane (c) component of

’’(Q,) is approximately 1.4 times larger than the in-plane (a/b) component at QAF.

Conversely, the much weaker even channel resonance is isotropic to within experimental

error, and the low energy response maintains a large gap (below 30meV) in the normal state.

While it is generally accepted that the neutron spin resonance is ubiquitous in at least the

hole-doped cuprates, recently two further collective magnetic modes have been observed in

HgBa2CuO4+δ. These Ìsing-like’ modes are very weakly dispersive and have the potential to

radically alter our view of the cuprates, if they are universally present. However, we find no

evidence for such modes in our sample of YBa2Cu3O6.9 in the energy range 10-60meV,

suggesting that such novel modes may in fact be peculiar to certain systems or are have

some other physical origin.


60

GROWTH AND CHARACTERIZATION OF

SUPERCONDUCTING ALLOYS. THE Ce DOPPED LaSb2 CASE

A. FENTE1, Roberto F. LUCCAS1, J. HANKO1, J. AZPEITIA1, M. A. RAMOS1, S.

VIEIRA1, M. GARCÍA-HERNÁNDEZ2, N. M. NEMES2 & H. SUDEROW1

1Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia

Condensada Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias Universidad Autónoma de Madrid, E-28049 Madrid, Spain

2Instituto de Ciencia de Materiales de Madrid, CSIC, Es-28049 Madrid, Spain


In this work we have synthesized high quality Ce doped LaSb2 single crystals and studied the

evolution of magnetic order when diluting the Ce ions. Results show a decrease in the

magnetic transition as the percentage of Ce is reduced, establishing the phase diagram of

La1-xCexSb2.


61

DIRECT VISUALIZATION OF SUPERCONDUCTING VORTEX

LATTICES UNDER A CONSTANT CURRENT FLOW

Ana MALDONADO1, I. GUILLAMÓN1,2, H. SUDEROW1, S. VIEIRA1, P.

RODIERE3, R. CÓRDOBA4, J. SESÉ4, J. M. DE TERESA4 & M. R. IBARRA4

1 Laboratorio de Bajas Temperaturas. Departamento de Física de la Materia Condensada. Instituto de Ciencia de Materiales Nicolás Cabrera. Facultad de Ciencias. Universidad

Autónoma de Madrid, 28049 Madrid, Spain.

2 H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK.

3 Institut Néel, CNRS / UJF, 25, Av. des Martyrs, BP166, 38042 Grenoble Cedex 9, France.

4 Instituto de Nanociencia de Aragón, Universidad de Zaragoza, 50009 Zaragoza, Spain.

References:

[1] A. Maldonado, I. Guillamón, H. Suderow and S. Vieira, Review of Scientific Instruments 82, 073710 (2011) "Scanning tunneling spectroscopy under large current flow through the sample" E-mail: [email protected]

We have developed a method to make scanning tunneling microscopy/spectroscopy imaging at very low temperatures while driving a constant electric current up to some tens of mA through the sample. It gives a new local probe, which we term current driven scanning tunneling microscopy/spectroscopy (CDSTM/S) [1]. Applications include local vortex motion experiments and local density of states studies. In this poster, the possibilities of this technique will be introduced by showing CDSTM/S studies in NbSe2 and W-based amorphous superconducting thin films. Both are the prototype systems to study the electronic structure of superconducting vortex cores and the dynamics of a two dimensional superconducting vortex lattice, respectively. Perspectives of applications will be also presented.


62

METAMAGNETIC TRANSITION IN UCoAl PROBED BY

THERMOELECTRIC MEASUREMENTS

Alexandra PALACIO, A. POURRET, G. KNEBEL, D. BRAITHWAITE,

D. AOKI, T. COMBIER & J. FLOUQUET

INAC, SPSMS, CEA Grenoble, 17 Rue des Martyrs, 38054 Grenoble, France


UCoAl is a heavy fermion compound with a metamagnetic transition from a paramagnetic ground state to a ferromagnetic state. For temperatures lower than TM= 11K, this metamagnetic transition is a first order transition that becomes a crossover above TM. The magnetization is related to the itinerant 5f electrons even if the U atoms present a local magnetic moment along the c-axis (the easy magnetization axis) because the orbital component is the main contribution to magnetism. In the ferromagnetic state a spontaneous magnetization occurs just above the metamagnetic transition with a total

magnetic moment of 0.3B per unit formula where B is the Bohr magneton. UCoAl is strongly anisotropic; when we apply a magnetic field along the c-axis, the metamagnetic transition occurs while when it is applied in the perpendicular direction, UCoAl presents a paramagnetic behaviour.

The interest in studying UCoAl comes from its relation with UGe2, a strongly correlated compound where ferromagnetism and superconductivity coexist. They both have a similar (T,P,H) phase diagram; the first order plane corresponding to the metamagnetic transition is divided into two wings under pressure and magnetic field which end in a Quantum Critical End Point (QCEP). The study of these wings is easier to perform in UCoAl rather than in UGe2 because in UCoAl they are present at ambient pressure. The second reason to perform thermoelectricity measurements in UCoAl is to determine the heat carrier type and its evolution through the metamagnetic transition.

We report thermopower field and temperature dependent measurements in UCoAl. In both, the external magnetic field is applied along the easy magnetization axis (c-axis). We extract information about the metamagnetic transition which is a first order transition at low temperatures and becomes a crossover at temperatures higher than the critical end point. The magnetic field dependent measurements also reveal that the number of heat carriers (hole type) increases significantly in the ferromagnetic state. Furthermore, comparing to Hall resistance measurements, we deduce that UCoAl is a multiband compound. The heavy hole band determined by thermopower measurements is drastically changed at the metamagnetic transition while the light electronic band determined by Hall measurements remains almost constant. Band structure calculations are in good agreement with these results and verify that UCoAl is a compensated metal. Finally, we also report measurements of the magnetic fluctuations around the metamagnetic transition by the Nernst effect and we analyse the longitudinal and transversal resistivity behaviours.


63

PRESSURE DEPENDENCE OF THE CRITICAL TEMPERATURE IN THE

2H TRANSITION METAL DICHALCOGENIDES

Manuel R. OSORIO1, P. RODIÈRE2, S. VIEIRA1 & H. SUDEROW1

1 Laboratorio de Bajas Temperaturas. Departamento de Física de la Materia

Condensada. Instituto de Ciencia de Materiales Nicolás Cabrera. Facultad de Ciencias.

Universidad Autónoma de Madrid, 28049 Madrid, Spain.

2Institut Néel, CNRS / UJF, 25, Av. des Martyrs, BP166, 38042 Grenoble Cedex 9, France.

References:

[1] L. N. Bulaevskii, Sov. Phys. Usp. 19, 836 (1976)

[2] V. G. Tissen, E. G. Ponyatovsky, M. V. Nefedova, A. N. Titov and V. V. Fedorenko,

Phys. Rev. B, 80, 092507 (2009)

[3] H. Suderow, V. G. Tissen, J. P. Brison, J. L. Martínez, S. Vieira, P. Lejay, S. Lee and S.

Tajima, Phys. Rev. B, 70, 134518 (2004)

[4] H. Suderow, V. G. Tissen, J. P. Brison, J. L. Martínez and S. Vieira, Phys. Rev. Lett. 95, 117006 (2005).


We present measurements of the critical temperature as a function of pressure in the

transition metal dichalcogenides 2H-TaSe2, 2H-TaS2 and 2H-NbS2, and find significant

increases of the critical temperature, Tc, in all compounds, with maxima lying between 10

GPa and 20 GPa. In 2H-TaSe2 and in 2H-TaS2, where superconductivity coexists with a

charge density wave and zero pressure, Tc is, respectively, 0.15 K and 1.5 K. The increase is

very significant, with Tc peaking around 8.5 K at 9 GPa in TaS2 and at 22.5 GPa in TaSe2. In

2H-NbS2, which has no charge density wave and Tc=6 K at zero pressure, we reached 19.8

GPa and Tc=8.9 K. We also present upper critical field measurements in 2H-NbS2, which

show an intricate dependence as a function of temperature, pointing out significant changes

of the Fermi surface (FS).



64

SUPERCONDUCTIVITY IN GE AND SI THROUGH Ga-ION

IMPLANTATION

Richard SKROTZKI1,2, T. HERRMANNSDÖRFER1, R. SCHÖNEMANN1,

V. HEERA1, J. FIEDLER1,3, E. KAMPERT1, F. WOLFF-FABRIS1,

P. PHILIPP1, L. BISCHOFF1, M. VOELSKOW1, A. MÜCKLICH1,

B. SCHMIDT1, W. SKORUPA1, M. HELM1 & J. WOSNITZA1

1 Dresden High Magnetic Field Laboratory (HLD) and Institute of Ion Beam Physics

and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany

2 Department of Chemistry and Food Chemistry, TU Dresden, Dresden, Germany

3 Experimental Physics, Institute of Physics, Ilmenau University of Technology,

Ilmenau, Germany

This work was supported by EuroMagNET, EU contract 228043.

References:

[1] T. Herrmannsdörfer et al., Phys. Rev. Lett. 102, 217003 (2009)

[2] R. Skrotzki et al., Low Temp. Phys. 37, 1098 (2011)

[3] R. Skrotzki et al., Appl. Phys. Lett. 97, 192505 (2010)


We report on two routes of embedding superconducting nanolayers in a semiconducting environment. Ion implantation and subsequent annealing have been used for preparation of superconducting thin-films of Ga-doped germanium (Ge:Ga) [1,2] as well as 10 nm thin amorphous Ga-rich layers in silicon (Si:Ga) [3]. Structural investigations by means of XTEM, EDX, RBS/C, and SIMS have been performed in addition to low-temperature and high-magnetic field electrical transport and magnetization measurements. Regarding Ge:Ga, we unravel the evolution of Tc with charge-carrier concentration concerning doping-induced superconductivity while for Si:Ga recently implemented nanostructuring allows for the occurrence of phase-coherent Josephson oscillations in out-of-plane oriented fields of up to 5 Tesla and temperatures below 5 Kelvin. This calls for potential onchip application in novel heterostructured devices.



65

SPECIFIC HEAT STUDY OF QUANTUM CRITICALITY

IN BaFe2(As1-xPx)2

Philip WALMSLEY1, L. MALONE1, C. PUTZKE1, S. KASAHARA2,

T. SHIBAUCHI2, Y. MATSUDA2 & A. CARRINGTON1

1University of Bristol, UK

2Kyoto University, Japan

References:

[1] “A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in

BaFe2(As1-xPx)2” K. Hashimoto, K. Cho, T. Shibauchi, S. Kasahara, Y. Mizukami, R.

Katsumata, Y. Tsuruhara, T. Terashima, H. Ikeda, M. A. Tanatar, H. Kitano, N. Salovich,

R. W. Giannetta, P. Walmsley, A. Carrington, R. Prozorov, Y. Matsuda, Science 336, 1554

(2012)

[2] “Evolution of the Fermi Surface of BaFe2(As1_xPx)2 on Entering the Superconducting

Dome” H. Shishido, A. F. Bangura3 A. I. Coldea, S. Tonegawa, K. Hashimoto, S. Kasahara,

P. M. C. Rourke, H. Ikeda,T. Terashima, R. Settai, Y. O¯ nuki, D. Vignolles, C. Proust, B.

Vignolle, A. McCollam, Y. Matsuda, T. Shibauchi, and A. Carrington, PRL 104, 057008

(2010)

The discovery of high Tc superconductivity in the Iron pnictide superconductors close to

(and in some cases coexistent with) a magnetic phase has prompted many comparisons to

the cuprate superconductors and added weight to the idea that high Tc superconductivity

requires proximity to some magnetic instability. Both the Iron pnictides and the cuprates

have a magnetic phase transition that tends towards zero temperatures as the system is

doped, with superconductivity arising in close proximity to the zero temperature intercept

of the phase transition. However the interplay between the magnetic and superconducting

phases is not fully understood key questions are unanswered such as whether magnetic

fluctuations provide the 'glue' that binds the Cooper pairs and whether quantum criticality

has a role in producing superconductivity in these systems.

With regard to the latter question, signs of quantum criticality have been recently reported

in the BaFe2(As1-xPx)2 system from measurements of the superfluid density (via penetration

depth)[1], electron mass (via de Haas van Alphen oscillations)[2] and susceptibility (via

NMR)[3]. In the present specific heat study we find a sharp peak in the size of the specific

heat anomaly at optimal doping in this system. Our findings are consistent with a large

enhancement of the electronic effective mass and provide an insight into multiband physics

in this material as well as the nature of quantum critical fluctuations at high temperatures.


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[3] “Unconventional Superconductivity and Antiferromagnetic Quantum Critical

Behavior in the Isovalent-Doped BaFe2(As1_xPx)2” Y. Nakai, T. Iye, S. Kitagawa, K. Ishida,

H. Ikeda, S. Kasahara, H. Shishido, T. Shibauchi, Y. Matsuda, T. Terashima, PRL 105,

107003 (2010)




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List of Participants

List of Participants

Aurora ALBERCA ICMM-CSIC, Madrid, Spain [email protected]

Pedro ALGARABEL ICMA-CSIC, Zaragoza, Spain [email protected]

Dai AOKI CEA-France and IMR, Japan [email protected]

Pegor AYNAJIAN Princeton University, USA [email protected]

Alexandre I. BUZDIN Université Bordeaux, France [email protected]

Agustín CAMÓN Universidad de Zaragoza, Spain [email protected]

Antony CARRINGTON University of Bristol, UK [email protected]

Amalia COLDEA University of Oxford, UK [email protected]

Eugenio CORONADO Universidad de Valencia, Spain [email protected]

Thomas CROFT University of Bristol, UK [email protected]

Julian DAICH INC, Madrid, Spain [email protected]

Enrique DÍEZ Universidad de Salamanca, Spain [email protected]

Fabienne DUC LNCMI, Toulouse, France [email protected]

Antón FENTE UAM, Madrid, Spain [email protected]

José L. FDEZ. CUÑADO UAM, Madrid, Spain [email protected]

Inês FIRMO Cornell University, USA [email protected]

Tobias FÖSTER HLD, Dresden, Germany [email protected]

José Augusto GALVIS UAM, Madrid, Spain [email protected]

Mar GARCÍA-HDEZ. CMM-CSIC, Madrid, Spain [email protected]

Luís GARCÍA-TABARÉS CIEMAT, Madrid, Spain [email protected]

Dianta GINTING Chukbuk National University, Korea [email protected]

Javier GLEZ. PÉREZ UAM, Madrid, Spain [email protected]



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Xavier GRANADOS ICMAB-CSIC, Barcelona, Spain [email protected]

Gael GRISSONNANCHE Université de Sherbrooke, Canada [email protected]

Isabel GUILLAMÓN University of Bristol, UK [email protected]

Francisco GUINEA ICMM-CSIC, Madrid, Spain [email protected]

M. Ricardo IBARRA UNIZAR-INA, Zaragoza, Spain [email protected]

Marcelo JAIME NHMFL-LANL, Los Alamos, USA [email protected]

Enno JOON NICPB, Tallinn, Estonia [email protected]

Konstantina

KONSTANTOPOULOU UPM, Madrid, Spain [email protected]

Prasanna KULKARNI UAM, Madrid, Spain [email protected]

Philippe LEBRUN CERN, Geneva, Switzerland [email protected]

Christopher LESTER University of Bristol, UK [email protected]

Liang LI WHMFC, Wuhan, China [email protected]

Roberto F. LUCCAS UAM, Madrid, Spain [email protected]

Jan Kees MAAN NFML, Nijmegen, The Netherlands [email protected]

Ana MALDONADO UAM, Madrid, Spain [email protected]

Ziad MELHEM Oxford Instruments, UK [email protected]

Aday José MOLINA UAM, Madrid, Spain [email protected]

Alexandra PALACIO CEA Grenoble/ SPSMS/IMAPEC [email protected]

Oliver PORTUGALL LNCMI, Toulouse, France [email protected]

Geert RIKKEN LNCMI, Grenoble, France [email protected]

Manuel RGUEZ. OSORIO UAM, Madrid, Spain [email protected]

José Gabriel RODRIGO UAM, Madrid, Spain [email protected]

Blanca SILVA FDEZ UAM, Madrid, Spain [email protected]

Richard SKROTZKI HLD, Dresden, Germany [email protected]

Hermann SUDEROW UAM, Madrid, Spain [email protected]

Javier TEJADA Universidad de Barcelona, Spain [email protected]

Masashi TOKUNAGA IMGSL-ISSP, Tokyo, Japan [email protected]

Johan VANACKEN INPAC, K.U. Leuven, Belgium [email protected]

Sebastián VIEIRA UAM, Madrid, Spain [email protected]


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Valerii VINOKUR ANL, Argonne, USA [email protected]

Peter WAHL MPI-FKF, Stuttgart, Germany [email protected]

Philip WALMSLEY University of Bristol, UK [email protected]

Jochen WOSNITZA HLD, Dresden, Germany [email protected]

Shunsuke YOSHIZAWA Tokyo Institute of Technology, Japan [email protected]

Documents

Abstract Book - inc.uam.es · Abstract Book . Science and Technology at High Magnetic Fields Miraflores de la Sierra, Madrid, 6-9 November, 2012 2 ... List of Participants ..... 67