I have presented my recent research "the magnetic structure of NiS2" at AOCNS (Asia-Oceania Conference on Neutron Scattering) on July 21, 2015, Manly Australia.

1. The magnetic structure of NiS2
S. Yano1, Chin-wei Wang1, Chun-Ming Wu1, J. S. Gardner, 1 Andrew Studer2, and
Despina. Louca3
1National Synchrotron Radiation Research Center, Neutron Group, Hsinchu 30077,
Taiwan
2 Bragg Institute, Australian Nuclear Science and Technology Organization,
Lucas Heights, New South Wales, 2234, Australia
3University of Virginia, Department of Physics, Charlottesville, VA 22904, USA
AOCNS 2015 Manly, Australia 7/21/2015

2. The phase diagram of NiS2-xSex
 Metal insulator transition is induced by Se doping or pressure
P.G. Nikolowitz et al. Phys. Rev. B. 77 (2008) 115135

3. 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.
The magnetic structure of NiS2-xSex
M. Matsuura et al. PRB 68 094409 (2003)
AFM M1 k = (0 0 0); 1st order
AFM M2 k = (1/2 1/2 1/2) 2nd order
 NiS2  NiS2-xSex

4. NOMAD@SNS, ORNL, U.S.A
The neutron scattering experiment
The Nanoscale-Ordered Materials
Diffractometer (NOMAD)
Purpose of the experiment
1. Magnetic structure
2. Local structure
 Powder samples
 Temperature dependence
 T = 2 to 150K
 NiS2-xSex
 x = 0, 0.4, 0.6, 0.8
What is the magnetic structure M1 and M2 anyway?

5. 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 

6. 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
Intensity(arb.units)
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
NiS2 Pa-3 (205) with Ni: 4a site(0 0 0)

7. The magnetic structure for M1
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
NiS2 Pa-3 (205) with Ni: 4a site(0 0 0)

8. To be compatible with M1, mM1i  mM2i= 0
Candidates for magnetic structure M2
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
T. Miyadai et al. JPSJ 38, (1975) 115

9. 1. The imaginary part of BV components
2. M1 and M2 are normal to each other mM1i  mM2j =0
Candidates for magnetic structure M2
M1(k = 000) M2
(k = 0.5 0.5 0.5)
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.
SARAh, A. S. Wills, Physica B, 276 (2000) 680.

10. The magnetic structure in NiS2
Г1 𝟁2, Г1 𝟁4
Г3 𝟁6
Г3 𝟁8
Г1 𝟁2
Г1 𝟁4
Г3 𝟁6
Г3 𝟁8

11. The four magnetic domains in NiS2
S.Yano et al. PRB submitted (2015)

12. Experiments with a single crystal of NiS2
5*5*5 mm3
Wombat (ANSTO)
SIKA (ANSTO, NSRRC)

13. Single crystal data from Wombat
M1
M2
 T = 60 K (Para)
Nuclear reflections
 T = 35 K (M1 phase)
Nuclear reflections
with magnetic peak at k = 000
(ex. (001), (110))
 T = 4 K (M2 phase)
Nuclear reflections
with magnetic peak at k = 0.5
0.5 0.5 (ex. (0.5 0.5 1.5))
and peak intensities at k =
000 are intensified.

14. The magnetic structure in NiS2
• 18 magnetic reflections
1 10 100 1000
1
10
100
1000
T = 4 K
Calclatedintensities
Observed intensities

15. The cold triple axis spectrometer SIKA
SIKA in User Program (2015, Mar) SIKA received operation
license (2015, June) see more at P013, Guochu Deng
Don’t for get next proposal round (2015 September 15)
Located at ANSTO-Bragg institute
J1 = 0.050 meV
J2 = 0.143 meV
D = 0.163 meV
MnF2

16. 28 29 30 31
0
1
2
3
4
(001) 
(110) 
Intensities(counts/monitor)
Temperature (K)
Critical scattering
1
2
3
4
(0.5 0.5 0.5)
0
1
2
3
4
(100)
(011)
Intensity(counts/monitor)
25 30 35 40 45
5
10
15
20
(111)
(200)
Temperature (K)
Background
M2
M2
M2
M1
Background
Nuclear
 M2 phase only
@(0.5 0.5 0.5) with β = 0.223(29)
@(1 1 1) with β = 0.219(54)
@(2 0 0) with β = 0.227(37)
38 40
0.4
0.6
0.8
(001)  0.313 (71)
(110)  0.252 (65)
Intensities(counts/monitor)
Temperature (K)
M1
M2
28 29 30 31
0
1
2
3
4
(0.5 0.5 0.5)

Intensity(counts/monitor)
Temperature (K)
28 29 30 31
5
10
15
20
(111) with 
(200)with 
Intensity(counts/monitor)
Temperature (K)
M. Matsuura et al. PRB 68 094409 (2003)
M1 β = 0.306(3) M2 β = 0.220(10)
 M1 + M2 phase
k = 0 0 0 @(1 0 0) β = 0.313(71)
@(0 1 1) β = 0.252(65)
k = 0.5 0.5 0.5
@(1 0 0) with β = 0.194(53)
@(0 1 1) with β = 0.246(50)

17.  The magnetic structure with powder
 M1; the structure is : k = (0 0 0) and Г1 𝟁1
 M2; the structure is k = (1/2 1/2 1/2) has four possible
magnetic structures.
 These two structure can coexist with mM1i  mM2j= 0. We
found the only 4 magnetic structure which might form
domains couldn’t be distinguished by neutron scattering.
 The magnetic structure with single crystal
 Wombat experiment
The powder model failed to explain 18 of magnetic
scattering intensities from k = 0.5 0.5 0.5@ T = 4K
 SIKA experiment
The order parameters tell me that we need to classify
magnetic scattering intensities with new eyes.
Summary
And, the mission continues ……..