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My approach to magnetism
- with Pair Distribution Function (PDF) analysis,
magnetic structural analysis,
and inelastic neutron scattering techniques
NSRRC, instrument scientist SIKA@ANSTO
Dr. Shinichiro Yano
Prof. Jun Akimitsu
“But please remember: This is only a work of fiction.
The truth, as always, will be far stranger.”
Arthur C. Clarke
“You can’t be a physicist by choosing to be a theorist. But you are
good at calculations, so I give you the subject which requires neutron
scattering. You need to be strong in both theory and experiment.”
Jun Akimitsu
Sheldon: Penny, I am a physicist. I have a working knowledge
of the entire Universe and everything it contains!
Penny : Who is Radiohead?
Sheldon : I have a working knowledge of the important things
in the Universe. (Big bang theory, season 2 )
How I became a experimental physicist.
Year Job Place Neutron
source
Material Experiences
2005-
2006
Undergrad
uate
Aoyama
-Gakuin
(Tokyo),
JRR3M CuB2O4 Thermal TAS
(Diffraction)
2006-
2008
Master Aoyama
-Gakuin
(Tokyo),
JRR3M, (Sr,Y)CoO3
MnP
Hard X-ray,
Thermal TAS
2008-
2012
Ph.D Aoyama
-Gakuin
(Tokyo)
JRR3M, J-
PARC
MnP
Ba2Mg2Fe12O
22
Earth quake,
Thermal TAS, Cold
TAS, Four circle,
Chopper
2012-
2014
Postdoc Univ. of
Virginia
NIST-NCNR,
SNS- ORNL,
HFIR-ORNL
LuMnO3,
NiS2-xSex
(La,Y)VO3
Chopper (SNS),
PDF machines,
Cold Chopper
(NIST)
2014
Nov.
- present
Instrument
scientist
NSRRC,
ANSTO
Bragg
institute
NiS2, MnP,
CoO, LuMnO3
Cold neutron TAS
SIKA
Year Job Place Neutron
source
Boss
2005-
2006
Undergrad
uate
Aoyama
-Gakuin
(Tokyo),
JRR3M
2006-
2008
Master Aoyama
-Gakuin
(Tokyo),
JRR3M,
2008-
2012
Ph.D Aoyama
-Gakuin
(Tokyo)
JRR3M, J-
PARC
2012-
2014
Postdoc Univ. of
Virginia
NIST-NCNR,
SNS- ORNL,
HFIR-ORNL
2014
Nov.
-present
Instrument
scientist
NSRRC,
ANSTO
Bragg
institute
Prof. Shinichi Itoh(KEK)
Prof. Louca Despina
(Univ. of Virginia)
Dr. J.S. Gardner (NSRRC)
Prof. Jun Akimitsu (Aoyama-Gakuin)
What is the structures?
◦ Crystal structure, Local structure, Magnetic structure
How do they behave?
◦ Diffuse scattering, spin wave, phonon, dynamic local
structure, crystal field excitation
Why is the magnetism?
The Study of Magnetism
What?
How?
Why?
What is the structures?
◦ Crystal structure, Local structure, Magnetic structure
How do they behave?
◦ Diffuse scattering, spin wave, phonon, dynamic local
structure, inelastic scattering
Why is the magnetism?
Magnetism – with PDF analysis
“He(Floyd) had already decided that X rays, sonic probes, neutron beams , and all other
nondestructive means of investigation would be brought into play before he called up the
heavy artillery of the laser. Clarke, Arthur C. 2001: A Space Odyssey
Bragg diffraction
(long range order)
Total scattering data
Reciprocal space
Fourier Transform
Pair density function (PDF) is obtained via Fourier transform of the normalized
elastic total scattering structural factor S(Q) (static PDF)
Rietveld refinement
Long-range periodic
structure (average structure)
Real-space refinement
Short-range structure
(local structure)
Rietveld vs PDF
Comprehensive understanding about structure
Ni-OO-O
Kinds of PDFs
Ready for 3 beams,
◦ Neutron = most common but very competitive
◦ X-ray = hottest now but resonances from Q = 30 Å-1
◦ Electron = most promising but needed to be commissioned
Ready for 3 methods with neutron scattering
◦ Static PDF
“Underneath the Bragg Peaks” by T.Egami and S.J.L.Billinge
◦ Dynamical PDF
Theory: T.Egami et al. (2012)
Experiment: Dmowski,(2008), Bing Li et al. (2014),
◦ Magnetic PDF
Experiment : Wu et al. (1987) B.A. Frandsen (2015)
Thoery and modeling : B.A. Frandsen (2014)(1st 2003, 2nd 2012)
Static PDF procedure
NOMAD@SNS
Bragg peaks are for Rietveld Analysis
PDFgetN: http://pdfgetn.sourceforge.net/
1 2 3 4
-2
0
2
4
6
G (
r)
r (A)
2K
30K
70K
100K
150K
200K
250K
300K
Average structure
(crystal structure)
Local structure
If Average structure explained
the pattern well, it means there
would be no local structure.
If Average structure did not explain
the pattern well, find out the local structure
x > 0.20, long range orbital order state disappear. Below TN,
G-SO phase in Y-rich region and C-SO phase in La-rich region
J.-Q Yan et al., Phys. Rev. B 84, 214405 (2011).
LaVO3
T = 143KG-type OO
C-type SO
YVO3
(T < TSO2)
C-type OO
G-type SO
LaVO3
G-type OO
C-type SO
The phase diagram of (Y,La)VO3
P21/a
P21/a
Pnma
Pnma
Pnma
Pnma
2.0 2.5 3.0 3.5 4.0 4.5 5.0-0.1
0.0
0.1
0.2
0.3
0.4
2.0 2.5 3.0 3.5 4.0 4.5 5.0
0.0
0.1
0.2
0.3
0.4
3.9 4.0 4.1 4.2 4.3 4.4 4.50.04
0.06
0.08
0.10
0.12
0.04
0.08
0.12
3.8 4.0 4.2 4.4
0.04
0.08
0.12
(e)
(d)(c)
r (Å)
r (Å)
PD
F (
Å-3
)
5 K 50 K
150 K 300 K
(a)
PD
F (
Å-3
)
Data at 150 K
P21/a model
Difference
(a)
Data at 250 K
Pnma model
Data at 250 K
P21/a model
Local structure YVO3The local G orbital pattern in P21/a
Y-O
V-O
0 50 100 150 200 250 300
3.99
4.02
4.05
4.08
4.11
2.0 2.5 3.0 3.5 4.0 4.5 5.0
0.0
0.1
0.2
0.3
0.4
0.5
5K Pnma model
300K Pnma model
(b)
(a)
O-O short
O-O long
Y0.7
La0.3
VO3
PD
F (
Å-3
)
-0.2
-0.1
0.0
0.1
0.2
0.3
O-O
pai
rs (
Å)
r(A)
Temperature (K)
TN
The new phase of local orbital ordering
The local C-OO was observed in
this system.
S.Yano et al., Phys. Rev. B 90, 214111 (2014).
What is the structures?
◦ Crystal structure, Local structure, Magnetic structure
How do they behave?
◦ Diffuse scattering, spin wave, phonon,
dynamic local structure inelastic scattering
Why is the magnetism?
Magnetism – with magnetic structure
“I think a good framework of thinking is physics. You know sort of the first principal of
reasoning. Boil things down to the fundamental truth, and reason up from there
When you wanna do something new, you have to apply physics approach. Physics is
the sort of figuring out how to find new things counterintuitive.”
Elon Musk.
Picture from TED
(2013)
Crystal structure symmetry (Space group)
Magnetic atoms
You have model??
2
2
, 2exp)()(69.2 3
i
ii
mag
Fehklhklmag rQQsQQfFI
Find the default values
Generate random values
for magnetic sites which
show low χ2
Magnetic point group theory Model Free
You need constraints?
i
calc
i
obs
i lkhFlkhF 22 )),,(),,((
The parameters are the number of magnetic atoms*3(x,y,z)
Neutron scattering intensities
Least square method
You got an answer!! Check your answers
1. Agree with physical picture
2. Add F=0 points as data, check χ2
3. Explain other experiment results?But, are you sure ??
S = Spins
q = The projection
of Spins
QsQ i
The phase diagram of NiS2-xSex
NiS2 cubic Pa-3 (No. 205)
Ni fcc structure at 4a (0, 0, 0)
P.G. Nikolowitz et al. Phys. Rev. B. 77 (2008) 115135
T. Miyadai et al. JMMM 31-34
(1983) 337-338
M2 disappear at around x = 0.3
M1 disappear between x = 0.6 and 0.8.
AFM M1 k = (0 0 0); 1st order
AFM M2 k = (1/2 1/2 1/2) 2nd order
NiS2-xSexAFM M1
1.0 1.5 2.0 2.5 3.0 3.5 4.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
0.8 1.0 1.2 1.4 1.6 1.8
0.4
0.6
0.8
1.0
1.2
T = 2 K
Inte
nsi
ty (
arb.
un
its)
N(222)
N(311)
N(220)
N(211)
N(210)
N(200)
N(111)
M1+M2 phase
M2 phase
M1 phase
M2(1/2 1/2 3/2)
M1(110)M1(100)
M2(1/2 1/2 1/2)
Q (Å-1)
The powder neutron diffraction NiS2
The magnetic structure for M1 Ni fcc with k = (0 0 0), M1: Г1 𝟁1(Ni = 1.0 mB at NiS2
Ma Mb Mc
0.577 0.577 0.577
0.577 -0.577 -0.577
-0.577 0.577 -0.577
-0.577 -0.577 0.577
To be compatible with M1, mM1i mM2i= 0
Candidate for magnetic structure M2
Ni fcc with k = (0 0 0) k = (1/2 1/2 1/2)
Ma Mb Mc
0.577 0.577 0.577
0.577 -0.577 -0.577
-0.577 0.577 -0.577
-0.577 -0.577 0.577
M1: Г1 𝟁1(Ni = 1.0 mB at NiS2
M1 and M2 are normal to each other mM1i mM2j= 0
Candidate for magnetic structure M2
M1 M2
Г1 𝟁1 Г1 𝟁1
Г1 𝟁2
Г1 𝟁3
Г1 𝟁4
Г3 𝟁5
Г3 𝟁6
Г3 𝟁7
Г3 𝟁8
Ex.) Г1 𝟁1(M1) Г1 𝟁2(M2)
Ma Mb Mc
6 6 6
6 -6 -6
-6 6 -6
-6 -6 6
Ma Mb Mc
4.732 -4.732 0
2.732 -2.732 5.464
0.732 2.732 2
-2.732 0.732 -2
= 0
Г1 𝟁2, Г1 𝟁4, Г3 𝟁6, or Г3 𝟁8 are possible.
The magnetic structure in NiS2
Г1 𝟁2, Г1 𝟁4
Г3 𝟁6, Г3 𝟁8,
The four magnetic domains in NiS2
S.Yano et al. PRB submitted (2015)
What is the structures?
◦ Crystal structure, Local structure, Magnetic structure
How do they behave?
◦ Spin wave, Diffuse scattering, phonon,
dynamic local structure, inelastic scattering
Why is the magnetism?
Magnetism – with inelastic neutron
“On principal, it is quite wrong to try founding theory on observable magnitude alone
In reality the very opposite happens. It is the theory which decides what we can observe.”
Albert Einstein.
The anomalous dispersion in MnP
Eq=70q2+0.4(meV)
Eq=145q2+0.4(meV)
Eq=86q3+0.4(meV)
We need to determine the dispersion relation of MnP in the
whole Brillouin zone
Y.Todate et al,J.Phys.Soc.Jpn., 56, 36 (1987)
Ferromagnetism phase
∝ q3 indicate unusual
energy excitation.
Inelastic Neutron Scattering@JRR3M
Single Crystal: 9mmΦ× 50 [mm3]
1. LTAS(Low Energy)
With high resolution
Ef fix : 3.0meV, T = 53K, LT
Collimation 10’ -80’-80’- open
2.TOPAN(Middle Range Energy)
Ei fix : 13.5meV, T = 53K,LT
Collimation 60’-60’-60’-60’
3.TAS-1(High Energy)
Ef fix : 14.7meV, T = 60K
Collimation B-80’-80’-B
2. TOPAN
1. LTAS
3. TAS-1
0.0
15
30
45
60
0 0.2 0.4 0.6 0.8 1
LTAS
TOPAN
TAS-1
E (
meV
)
(h,0,0)
Magnetic Excitations in MnP@TAS’s
High energy and
High resolution
0.0
2.0
4.0
6.0
8.0
0 0.1 0.2 0.3 0.4
LTASTOPANTAS-1
E (
meV
)
(h,0,0)
1. 2 branches ?
2. Clear discrepancy from q3 model
Eq=86q3+0.4(meV)
The character of HRC:HRC delivers high-resolution and
relatively high-energy neutrons for
a wide range of studies on the dynamics of materials.
Vacuum Camber
High Resolution Chopper Spectrometer
The detectors cover -10 to 40°(The design was -31 to 124°)
PSD detector
DAQ-middleware system for HRC
DAQ electronics
33 of Neunet
Storage
Device
CPU+Labview program (by Satoh)DAQ-middleware
On-Off
PSD
Event data are stored in
/home/daq/hrc/
256 of Position
Sensitive Detector
Schematic configuration neutron path
qa = ki cosy − kf cos (fH − y) cosfV,
qb= ki siny + kf sin (fH − y) cosfV ,
qc = ki sinfV,
Scan trajectories on a chopper spectrometer in energy-momentum space.
Measurements of excitations in a one-dimensional system and a three-
dimensional system.
Neutron Inelastic Scattering
Analysis of 4 Dimensional E-Q Spacea*-b*(Qc=0:-~+) b*-E
a*-c*(Qb=2:2-~2+) c*-E
3
2
1
Qb
(rl
u)
-1 0 1Qa (rlu)
(a)
3
2
1
Qb
(rl
u)
3020100E (meV)
(b)
-1
0
1
Qc (
rlu
)3020100
E (meV)
(d)
-1
0
1
Qc (
rlu
)
-1 0 1Qa (rlu)
(c)
MnP
Figure: Dispersion relation of the spin waves in the ferromagnetic phase of MnP
along the a* and b*-axis. We assumed isotropic 6th exchange parameters and
calculated dispersion relation using the Heisenberg model for 2-sub lattices.
Spin waves in MnP
J1 = 0.377 ±0.14, J2 = 0.657 ±0.10, J4 = 0.067 ±0.13,
J5 = 0.267±0.10, and J6 =0.647 ±0.08 meV
Takeuchi and Motizuki discussed a mechanism of the transition
from the ferromagnetic phase to the proper screw spiral phase,
Helimagnetism and Exchange Interaction
J4 0
,
The obtained exchange constants in the ferromagnetic phase of MnP as listed in
Table 2 satisfy the conditions in eqs (1), (2), (3) and the condition in eq. (4) is
not satisfied.
J2/J
41
J6 cos
9
J
4
2 0
J1 2J
5 2cos
9
J4
…(1)
…(2)
…(3)
…(4)
S.Takeuchi and K.Motizuki J.Phys.Soc.Jpn 27 No.4 742 (1967)
J1 = 0.377 ±0.14, J2 = 0.657 ±0.10, J4 = 0.067 ±0.13,
J5 = 0.267±0.10, and J6 =0.647 ±0.08 meV
: Mn
: O
: R
ab
c
Hexagonal RMnO3
(Y, Lu, Ho, Yb)
Space group P63cm
High TC ~ 1000 K
TN ~100 K (LuMnO3 = 86 K)
Mn3+ forms triangular lattice
N.N. = 3.48Å
z=0
z=0.5G4 representation
Crystal structure of RMnO3
A. Munoz et al. PRB 62 9498(2000)
P. Tong et al. PRB 86 094419(2012)
S. Lee et al. Nature 451 805(2008)
DCS@NCNR(U.S.A)
=4.5 Å. dE = 0.142meV
Q range 0.12 - 2.6 Å-1
with 40g of powder sample
Q(Å-1)(a) At 4 K under TN, it is barely present.
(b) At 100 K just above TN,the scattering is intensified
(c) At 180 K above TN, it subsides, but still exists up to 250 K.
70 75 80 85 90 950
50
100
150
Inte
gra
ted
inte
nsity a
t (1
01)
Temperature (K)
2b0.403TN 87.9K
The magnetic scattering at (101)
The magnetic intensity at (101) follows a
power law dependence,
which is typical of 2D AFM systems
𝐼 ∝𝑇
𝑇𝑁− 1
2𝛽
𝑤𝑖𝑡ℎ 𝛽 = 0.20Q ~ 1.20, 2.40 Å-1 are correspond
to Mn-Mn N.N. and N.N.N.,
Lorentzian functionAsymmetric
Symmetric
T ~TN
T >>TN
Warren 2D
Connection between FE and 2D
TN, where all glide and mirror planes are eliminated
P. Tong et al. PRB 86 094419(2012)
Mn-O3-Mn ≠ 120 degree.
Release magnetic frustration
Local structure
P63cm -> P63
What is the structures?
◦ Crystal structure, Local structure, Magnetic structure
How do they behave?
◦ Diffuse scattering, spin wave, phonon, dynamic local
structure
Why is the magnetism?
Magnetism@ ANSTO, NSRRC
“Tactics is knowing what to do when there is something to do; strategy is knowing what
to do when there is nothing to do. Why? Turns Tacticians into Strategists”
Garry Kasparov
Cold Triple axis in the world
LTAS, C11
(stopped, JRR3M)
CTAS
(under commission, HANARO)
SIKA
(will start user commission)
CHINA
(construction, CARR)
PANDA
(Germany FRM-II)IN14
(Frence ILL)
SIKA will be very important
1. Only one Cold TAS starts user program in Asia-Oceania area soon
2. Neutron flux at sample position is (will be) good
MACS, SPINS
(NIST,NCNR)CTAX
(HIFR,ORNL)
Why we need Cold TAS Interactive (with chopper at spallation source)
The magnetic scattering (magnetic form factor)
The environment (with H, P, T, and polarized neutrons)
0.1 1 10
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Momentum Space Q (Å-1
)
Mn
Man
get
ic F
orm
fac
tor
F(Q
)2
0.01
0.1
1
10
100
1000
En
ergy
(meV
)
Chopper
Thermal TAS
Cold TAS
To the future
“Intelligence should be viewed as a physical process that tries to maximize future freedom
action and avoids the constraints its own future.”
Alex Wissner Gross.
𝐹 = 𝑇 𝛻 𝑆𝜏
𝑃𝑡ℎ𝑖𝑠 𝑐𝑦𝑐𝑙𝑒 = 𝑅𝑚𝑒 + 𝑅𝑢𝑠𝑒𝑟𝑠(𝑆𝑢, 𝑆𝑠, ) 𝛻𝑅𝐴𝑂𝐶𝑛𝑒𝑥𝑡 𝑐𝑦𝑐𝑙𝑒
Intelligence is a force F that acts with
T = reservoir temperature (strength)
S = the entropy associate with microstate
(𝛻 𝑆 = Diversity of possible accessible futures)
𝜏 = up to future time horizon PRL 110 168702 (2013)
Picture from TED
The magnetic structure of NiS2 in single crystal
◦ Wombat, Koala (2015, Jan.)
◦ SIKA (2015, Jun.)
The superconductivity on MnP
◦ D20, D23 in ILL, France (2015, Dec.)
◦ SIKA (2015, Aug)
◦ J-PARC, Japan (2016?)
The multiferroic of (Lu,Y)MnO3
◦ Pelican (2015, Nov.)
◦ NOMAD ORNL, U.S.A (2015, Sep.)
Magnetism
“Science is made by men, a self-evident fact that is far too often forgotten”
Werner Heisenberg