Crystal and magnetic structures of Y2CrS4

Article abstract of DOI:10.1016/j.jpcs.2007.08.016

Chromium(II) sulfide, Y₂CrS₄, prepared by a solid-state reaction of Y₂S₃ and CrS, showed an antiferromagnetic transition at 65 K. The neutron diffraction patterns at 10 and 90 K were both well refined with the space group Pca2₁. At 90 K, cell parameters were a=12.5518(13) ?, b=7.5245(8) ?, and c=12.4918(13) ?. At 10 K, magnetic peaks were observed, which could be indexed on the same unit cell. Magnetic moments of chromium ions were parallel to the b-axis and antiferromagnetically ordered in each set of the 4a sites.

Full text of DOI:10.1016/j.jpcs.2007.08.016

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Journal of Physics and Chemistry of Solids 68 (2007) 2133–2137
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Crystal and magnetic structures of Y CrS4
2
a,
Keitaro Tezuka , Yue Jin Shan , Hideo Imoto , Kenji Ohoyama
Ã
a
a
b
a
Department of Applied Chemistry, Faculty of Engineering, Utsunomiya University, Utsunomiya, Tochigi 321-8585, Japan
b
Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577, Japan
Abstract
Chromium(II) sulfide, Y
The neutron diffraction patterns at 10 and 90 K were both well refined with the space group Pca2
2
CrS
4
, prepared by a solid-state reaction of Y
2
S
3
and CrS, showed an antiferromagnetic transition at 65 K.
. At 90 K, cell parameters were
1
˚
˚
˚
a ¼ 12.5518(13) A, b ¼ 7.5245(8) A, and c ¼ 12.4918(13) A. At 10 K, magnetic peaks were observed, which could be indexed on the same
unit cell. Magnetic moments of chromium ions were parallel to the b-axis and antiferromagnetically ordered in each set of the 4a sites.
r 2007 Elsevier Ltd. All rights reserved.
Keywords: A. Chalcogenides; C. Neutron scattering; D. Crystal structure; D. Magnetic properties; D. Magnetic structure
1
. Introduction
in a flow of the mixed gas of CS and N which was
2 2
obtained by bubbling the N gas through liquid CS at
2
2
4
Divalent chromium ions are Jahn–Teller ions with d
room temperature. Chromium sulfide was synthesized by
heating the mixture of chromium and sulfur at 1000 1C in
an evacuated silica tube. The starting materials were
stoichiometrically mixed together and sealed in an evac-
uated silica tube. The tube was heated at 1300 1C for 24 h.
Powder X-ray diffraction (XRD) patterns were mea-
sured with Cu Ka radiation on a RINT2000 diffractometer
(Rigaku) equipped with a graphite monochromator.
The magnetic susceptibilities were measured under an
applied field of 0.1 T in the temperature range between 4.5
and 300 K by using a SQUID magnetometer (Quantum
Design, MPMS-5S).
Powder neutron diffraction measurements were carried
out using the Kinken powder diffractometer for high-
efficiency and high-resolution measurements, HERMES,
of Institute for Material Research, Tohoku University,
installed at the JRR-3M reactor in Japan Atomic Energy
configuration. They make complex sulfides with other
cations but these sulfides have not been well studied. One
of the examples is Er CrS , having an orthorhombic
2
4
structure belonging to the space group Pca2 (No. 29)
1
1,2]. The results of the structure refinement suggested that
[
CrS6 octahedra in this structure were distorted by the
Jahn–Teller effect. Other rare-earth elements were also
reported to form R CrS (R ¼ Y, Ho–Tm) that crystallized
2
4
in the same structure [3,4], though their detailed crystal
structures were not investigated. Electronic properties have
not been studied for any of these compounds. Since the
yttrium ion is diamagnetic, Y CrS is suitable for the
2
4
investigation of magnetic behavior of chromium ions in
Er CrS -type compounds. In this study, we investigated the
crystallographic and magnetic properties of Y CrS .
2
4
2
4
Agency (JAEA), Tokai. Neutrons with wavelength of
˚
2
. Experimental
Y CrS was prepared by a solid-state reaction. Yttrium
sulfide (Y S ) and chromium sulfide (CrS) were used as
1
.81430 A were obtained by the 331 reflection of the Ge
monochromator and 120-blank-220 collimation [5]. The
sample was set in a 10 mm diameter vanadium cylinder,
which was sealed in a standard aluminum cell under a
helium gas and cooled with a liquid helium cryostat.
Intensity data from 31 to 1451 were used in the crystal
structure and magnetic structure refinements using Riet-
veld method program RIETAN [6].
2
4
2
3
starting materials. In order to obtain yttrium sulfide,
yttrium oxide (Y O ) was heated in a silica boat at 1000 1C
2
3
Ã
Corresponding author. Tel.: +81 28 689 6174.
E-mail address: ktez@cc.utsunomiya-u.ac.jp (K. Tezuka).
0022-3697/$ - see front matter r 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jpcs.2007.08.016

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K. Tezuka et al. / Journal of Physics and Chemistry of Solids 68 (2007) 2133–2137
2134
3
. Results and discussion
Er CrS being used as the initial parameters. The lattice
2 4
parameters for Y CrS
2
were determined to be
4
˚
˚
˚
3
.1. Crystal structure
a ¼ 12.5686(3) A, b ¼ 7.5548(2) A, and c ¼ 12.4942(3) A.
The refined results are shown in Table 1 and Fig. 1. Fig. 2
shows the crystal structure of Y CrS . Bond lengths
Y CrS prepared in this study is formed in a single
2
4
2
4
phase. The powder X-ray diffraction pattern was success-
fully analyzed with an orthorhombic unit cell, space group
Pca2 (No. 29) by the Rietveld method, the structure of
between Cr and S calculated from the refined data are
shown in Fig. 3. The two bonds for each Cr were
considerably longer than the other four bonds. These
indicate that CrS6 octahedra are distorted due to the
1
Table 1
Crystallographic data for Y
2
CrS
4
at room temperature
Space group
1
Pca2 (No. 29)
˚
a (A)
12.5686(3)
7.5548(2)
12.4942(3)
7.67
˚
b (A)
˚
c (A)
R
s
wp (%)
Cr1S6
1.71
Atoms
x
y
z
Cr1
Cr2
Y1
Y2
Y3
Y4
S1
0.3798(7)
0.3966(6)
0.3802(5)
0.6335(5)
0.3815(5)
0.6391(4)
0.888(2)
0.387(2)
0.8912(9)
0.8638(9)
0.3793(9)
0.3650(8)
0.598(2)
0.602(2)
0.880(3)
0.8879(15)
0.114(2)
0.137(2)
0.371(3)
0.364(2)
0.1863(7)
0.8131(9)
0.813
Y
0.0115(4)
0.1699(4)
0.9921(5)
0.1222 (11)
0.8624(14)
0.0035(11)
0.7311(10)
0.1253(15)
0.8641(12)
0.9759(11)
0.7326(9)
Cr2S6
0.5386(11)
0.5201(12)
0.2863(10)
0.7693(8)
0.5111(12)
0.5427(11)
0.2964(9)
0.7433(10)
S2
S3
S4
S5
c
S6
S7
S8
b
a
Note: All atoms were in 4a sites. All isotropic atomic displacement
2
parameters (B) were fixed to be 0.3 A .
˚
Fig. 2. Crystal structure of Y CrS .
2
4
1
1
1
1
6000
4000
2000
0000
8
6
4
2
000
000
000
000
0
1
0
20
30
40
50
60
70
80
90
100
110
120
130
2
θ / °
2 4
Fig. 1. Powder X-ray diffraction pattern fitting for Y CrS . The calculated and observed patterns are shown on the top solid line and the cross markers,
respectively. The vertical marks in the middle show positions calculated for Bragg reflections. The lower trace is a plot of the difference between calculated
and observed intensities.

ARTICLE IN PRESS
K. Tezuka et al. / Journal of Physics and Chemistry of Solids 68 (2007) 2133–2137
2135
S1
S8
3
.07(2) Å
2.79(2) Å
S4
.55(2) Å
2
.49(2) Å
2.52(2) Å
2
2
.57(2) Å
.60(2) Å
S5
S1
Cr2
S3
S8
Cr1
2
2
.33(2) Å
S7
S6
2.39(2) Å
S2
2
.43(2) Å
2
.85(2) Å
2.71(2) Å
S6
S4
Fig. 3. Distortions of CrS
6
octahera.
Table 2
0
0
0
.06
.04
.02
1
00
2 4
Cell parameters for Y CrS
˚
a (A)
˚
b (A)
˚
c (A)
T (K)
7
5
2
5
0
5
0
RT
12.5686(3)
12.5518(13)
12.543(2)
7.5548(2)
7.5245(8)
7.5223(9)
12.4942(3)
12.4918(13)
12.492(2)
9
1
0
0
0
100
200
T / K
300
Jahn–Teller effect of divalent chromium ions, similar to
those in Er CrS .
The neutron diffraction patterns at 10 and 90 K were
2
4
both well refined with the space group Pca2 (No. 29) by
1
ZFC
FC
using atomic positions in Table 1. At 90 K, lattice
˚
parameters were determined to be a ¼ 12.5518(13) A,
˚
˚
b ¼ 7.5245(8) A, and c ¼ 12.4918(13) A. At 10 K, lattice
˚
0.00
parameters were determined to be a ¼ 12.543(2) A,
˚
˚
0
100
200
300
b ¼ 7.5223(9) A, and c ¼ 12.492(2) A. The lattice para-
meters are listed in Table 2. The lattice parameters in this
sulfide increased with increasing temperatures.
T / K
Fig. 4. Magnetic susceptibility vs. temperature for Y . The inset
shows the inverse magnetic susceptibilities as a function of temperature.
2
CrS
4
3
.2. Magnetic property
Magnetic susceptibilities were measured in the tempera-
ture range between 4.5 and 300 K. Fig. 4 shows tempera-
ture dependence of magnetic susceptibilities for Y CrS .
respectively. The effective magnetic moments indicated
4
that chromium ions had 3d high-spin state. The Weiss
2
4
Antiferromagnetic anomaly was observed at 65 K. The
susceptibility obeyed the Curie–Weiss law above 200 K.
The effective magnetic moment was experimentally deter-
constant was determined to be a positive value, 28.2(8) K
though antiferromagnetic behavior was observed. Differ-
ences between ZFC and FC were observed below Neel
´
mined to be 4.69(1) m from the Curie–Weiss fitting. The
temperature. These results suggest that the magnetic
moments of Cr in Y CrS order with a slight ferromagnetic
component below Neel temperatures.
´
B
2
theoretical effective magnetic moments of Cr in the high-
+
2
4
spin state and in the low spin state, are 4.90 and 2.83 mB,

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K. Tezuka et al. / Journal of Physics and Chemistry of Solids 68 (2007) 2133–2137
2136
3.3. Magnetic structure
In order to determine the changes in its magnetic
structures at the magnetic transition, neutron diffraction
measurements were performed above and below T , 90
N
1
0 K
and 10 K. At 10 K, several additional Bragg peaks were
observed indicating magnetic ordering as shown in Fig. 5.
These magnetic peaks could be indexed on the same
crystallographic unit cell. Thus, superlattice or satellite
peak was not observed. This indicates that the magnetic
propagation vector is a null vector [0, 0, 0]. Under this
condition, the possible magnetic structure of the 4a site of
space group was estimated by the representation analysis
technique (program SARAh [7]).
9
0 K
5
10
15
θ / ˚
20
25
2
Fig. 5. Powder neutron diffraction patterns of Y
0 K. Indices for magnetic reflections are based on crystallographic unit
cell.
2 4
CrS at (a) 10 K and (b)
9
The structure contains two kinds of chromium sites, Cr1
and Cr2, both of them occupying the 4a Wyckoff positions
of the orthorhombic space group Pca2 . We first discuss
1
the magnetic arrangement of Cr1 ions. Their positions are:
Position
x
y
z
Cr1
Cr11
Cr12
Cr13
Cr14
0.3798(6)
0.6202(6)
0.8798(6)
0.1202(6)
0.888(2)
0.112(2)
0.112(2)
0.888(2)
0.1863(7)
0.6863(7)
0.1863(7)
0.6863(7)
Cr2
The Cr1 ions have respective magnetic moments S , S ,
2
1
S , and S , and four types of magnetic arrangements are
3
4
possible:
c
F ¼ S þ S þ S þ S
1
2
3
4
A1 ¼ S1 þ S2 ꢀ S3 ꢀ S4
A2 ¼ S1 ꢀ S2 þ S3 ꢀ S4
A3 ¼ S ꢀ S ꢀ S þ S
b
a
Fig. 6. Magnetic structure of Y CrS
2
4
at 10 K.
1
2
3
4
8
6
4
2
000
000
000
000
0
1
0
20
30
40
50
60
70
80
θ / °
90
100 110 120 130 140
2
Fig. 7. Powder neutron diffraction pattern fittings for Y
2
4
CrS at 10 K. The calculated and observed patterns are shown on the top solid line and the cross
markers, respectively. The first vertical marks in the middle show positions calculated for nuclear Bragg reflections. The second vertical marks show
positions calculated for magnetic reflections. The lower trace is a plot of the difference between calculated and observed intensities.

ARTICLE IN PRESS
K. Tezuka et al. / Journal of Physics and Chemistry of Solids 68 (2007) 2133–2137
2137
The calculation of the representation analysis showed
that different sets of magnetic modes were possible, i.e.,
for the irreducible representation G with the A2 , A3 ,
intensities due to the ferromagnetic diffractions are
too weak compared with those due to the nuclear
diffraction, and the component of the magnetic moment
with F-type could not be estimated. It seems most probable
that the ferromagnetic component is parallel to the x-axis
because the Fx mode transforms according to the
1
x
y
and A1 modes; G with the A3 , A1 , and F modes; G
z
2
x
y
z
3
with the F , A1 , and A3 modes; and G with the A1 , F ,
x
y
z
4
x
y
and A2z modes (the subscripts show the direction of
magnetic moments). Cr2 ions also could be discussed in
the same way and the combinations of the magnetic
arrangements of Cr1 and Cr2 ions gave a large number
of possibilities. Then, we assumed that the ordered
magnetic moments of chromium ions at the two sets of
irreducible representation G , to which the arrangement
3
of the antiferromagnetic moments belongs. The refined
2
+
magnetic moment of Cr
is 3.27(9) m , which is slightly
B
4
smaller than 4 mB expected from the 3d electronic
configuration.
4
a sites had the same magnitude and adopted a collinear
arrangement. This assumption led to a successful Rietveld
refinement giving the magnetic structure shown in
Fig. 6. The result of powder neutron pattern fitting
by using this magnetic structure is shown in Fig. 7. In
this structure, magnetic moments of chromium ions
order antiferromagnetically in each set of the 4a sites.
The directions of all magnetic moments are parallel to
the b-axis, i.e, the A1 mode dominates for Y CrS at
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