Magnetic phase diagram of CrTe1-xSbx (0.0≤x≤1.0)

Article abstract of DOI:10.1016/S0925-8388(99)00244-3

Measurements of the high field magnetization of CrTe_1-xSb_x (0.0≤x≤1.0) were carried out at 4.2 K in pulsed magnetic fields up to 300 kOe. The temperature dependence of the magnetization of CrTe_1-xSb_x was measure

Full text of DOI:10.1016/S0925-8388(99)00244-3

Journal of Alloys and Compounds 290 (1999) 25–29
L
Magnetic phase diagram of CrTe Sb (0.0#x#1.0)
1
2x
x
a
a
a
b
b
b
b
N. Suzuki , T. Kanomata , R. Konno , T. Kaneko. , H. Yamauchi , K. Koyama , H. Nojiri ,
b
b
Y. Yamaguchi , M. Motokawa
a
Faculty of Engineering, Tohoku Gakuin University, Tagajo 985-8537, Japan
b
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Received 10 May 1999
Abstract
Measurements of the high field magnetization of CrTe12xSb (0.0#x#1.0) were carried out at 4.2 K in pulsed magnetic fields up to
x
3
00 kOe. The temperature dependence of the magnetization of CrTe12xSb was measured in the temperature range from 4.2 K to 800 K.
x
The magnetic phase diagram of CrTe12xSb (0.0#x#1.0) was determined, which is similar to the typical one for the mixed crystals of the
x
layered antiferromagnetic and ferromagnetic compounds proposed by de Gennes.
 1999 Elsevier Science S.A. All rights reserved.
Keywords: CrTe12xSb ; magnetization curve; magnetic phase diagram
x
1
. Introduction
The transition metal compounds CrTe and CrSb crys-
tallize in the hexagonal NiAs-type crystal structure as
shown in Fig. 1. CrTe is a metallic ferromagnet with the
Curie temperature TC of about 340 K. The magnetic
moment of CrTe at 4.2 K was reported to be about 2.5 mB
per formula unit. The magnetic properties of CrTe have
attracted much interest because of its very large magneto-
volume effect [1–5]. Ohta et al. reported that the Curie
temperature TC of CrTe decreases linearly with pressure
and its value of the pressure derivative ≠T /≠p is 27.0 K
C
2
1
kbar [6].
On the other hands, CrSb is a metallic antiferromagnet,
consisting of ferromagnetic planes perpendicular to the
c-axis, which are antiferromagnetically coupled. According
to neutron diffraction measurement, the magnetic moment
per Cr atom is 2.7 mB [7]. The N e´ el temperature TN of
CrSb is about 700 K. The recent results of band calcula-
tions and photoemission spectroscopy measurement show
that these compounds are itinerant electron magnetic
compounds [8–12].
The magnetic phase diagrams of CrTe12xSb (0.0#x#
x
1
.0) were previously reported by Takei et al. [13] and
Grazhdankina and Zainullina [14]. Their diagrams are not
in agreement with each other.
The aim of this paper is to refine the magnetic phase
E-mail address: kanomata@tjcc.tohoku-gakuin.ac.jp (T. Kanomata)
Fig. 1. Crystal structure of CrTe12xSbx (0.0#x#1.0).
0
925-8388/99/$ – see front matter
 1999 Elsevier Science S.A. All rights reserved.
PII: S0925-8388(99)00244-3

2
6
N. Suzuki et al. / Journal of Alloys and Compounds 290 (1999) 25–29
diagram of CrTe12xSb (0.0#x#1.0) by magnetic mea-
x
surements.
2
. Experiments
Polycrystalline samples of CrTe12xSbx (0.0#x#1.0)
were prepared from powders of Cr (99.9%), Te
99.9999%) and Sb (99.99%). They were mixed in the
(
desired proportion, sealed in evacuated silica tubes and
heated at 9008C for 7 days and then quenched in water.
The reaction products were pulverized, mixed and heated
at 9008C for 7 days and then quenched.
The X-ray diffraction lines of the prepared samples were
indexed with the hexagonal NiAs-type structure. The
˚
lattice parameters were found to be a53.999 A, c56.240
˚
˚
˚
A for CrTe and a54.129 A, c55.470 A for CrSb. These
results are consistent with those previously reported by
Takei et al. [7], Grazhdankina and Bersenev [3], Ido et al.
Fig. 3. The unit-cell volume V and the axial ratio c/a versus con-
centration x at room temperature for CrTe12xSb . The closed circles show
x
unit-cell volume V and the open circles axial ratio c/a.
[1], Lotgering and Gorter [15] and Nagasaki et al. [16].
The concentration dependence of the lattice parameters
a and c at room temperature for CrTe12xSb is shown in
temperature dependence of the magnetization s of the
x
Fig. 2. The open circles show the lattice parameter a and
the closed circles the lattice parameter c. The lattice
parameter a increases with increasing Sb concentration. On
the other hand, the lattice parameter c decreases with
increasing x. The unit-cell volume V and the axial ratio c/a
CrTe12xSb powdered samples were measured at 10 kOe
x
by a pendulum type magnetometer and vibrating sample
magnetometer (VSM) in the temperature range from 4.2 K
to 800 K. The measurements of high field magnetization at
4.2 K were carried out by an induction method in pulsed
magnetic fields up to 300 kOe.
of CrTe12xSb are shown as function of concentration x in
x
Fig. 3. The closed circles show the unit-cell volume V and
the open circles show the axial ratio c/a. As shown in the
figure, the unit cell volume V and the axial ratio c/a
decrease with increasing x.
3. Results and discussions
The magnetic transition temperatures were determined
by measuring the temperature dependence of the AC initial
permeability m using an AC transformer method. The
Fig. 4(a) and (b) show the temperature dependence of
the initial permeability m for CrTe and CrTe0.6Sb0.4
,
respectively. As seen in the figure, the initial permeability
of CrTe decreases sharply with temperature around 330 K.
The Curie temperature was defined as the intersection
point of the two lines, as shown by an arrow in the figure.
The Curie temperature is found to be 343 K. This value is
in good agreement with 342 K given by Grazhdankina and
Zainullina [14] but somewhat smaller than 350 K reported
Ohta et al. [6]. The m 2 T curve of CrTe0.6Sb0.4 has an
anomaly around 125 K below the Curie temperature T 5
C
2
50 K. The temperature of the anomaly Tt1 corresponds to
the canted-ferromagnetic transition as mentioned below. A
similar anomaly is also observed around 110 K for CrTe0.7
Sb0.3
.
Fig. 5(a) and (b) show the high field magnetization
curves of CrTe12xSb with 0.0#x#0.2 and 0.3#x#0.9 at
x
4
.2 K in magnetic fields up to 300 kOe, respectively. As
seen in Fig. 5(a), the magnetization of samples with x5
.0, 0.1 and 0.2 is saturated at about 30 kOe. The
0
magnetization of samples with 0.3#x#0.9 is not saturated
in the magnetic fields up to 300 kOe, and the mag-
netization decreases rapidly with increasing x. The samples
Fig. 2. Lattice parameters a and c versus concentration x at room
temperature for CrTe12xSb . The open circles show lattice parameter a
x
and the closed circles lattice parameter c.

N. Suzuki et al. / Journal of Alloys and Compounds 290 (1999) 25–29
27
Fig. 5. (a) Magnetization curves at 4.2 K for CrTe12xSb (0.0#x#0.2).
Fig. 4. (a) Temperature dependence of the initial permeability m for
CrTe. (b) Temperature dependence of the initial permeability m for
x
(
b) Magnetization curves at 4.2 K for CrTe12xSbx (0.3#x#0.9).
CrTe0.6Sb0.4
.
with x50.8 and 0.9 are assumed to be antiferromagnetic at
4
.2 K because CrSb is an antiferromagnet.
The high field susceptibility was determined from the
linear part of high field magnetization curve. The con-
centration dependence of the high field susceptibility xhf
for CrTe12xSb (0.0#x#0.7) at 4.2 K is shown in Fig. 6.
x
xhf increases linearly with increasing x up to x¯0.2 and
then increases drastically with x from x50.3 to 0.7. So the
ferromagnetic structure is considered to change to a canted
structure at x¯0.2. Indeed Takei et al. reported previously
neutron diffraction measurement [13] that CrTe0.75Sb0.25
has a canted structure.
Fig. 7(a) and (b) show the temperature dependence of
the magnetization s at 10 kOe of CrTe12xSb with 0#x#
x
0
.2 and 0.3#x#0.7 which are ferromagnetic and canted at
low temperature, respectively. The temperature where the
magnetization disappears, corresponds to the Curie tem-
Fig. 6. The concentration x dependence of high field susceptibility xhf for
CrTe12xSbx (0.0#x#0.7) at 4.2 K.

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8
N. Suzuki et al. / Journal of Alloys and Compounds 290 (1999) 25–29
Fig. 8. Magnetic phase diagram of the CrTe12xSb . s, n from mag-
x
netization and permeability measurements, respectively and j from
thermal expansion measurements.
from ferromagnetic to canted and then to antiferromagnetic
with increasing x at low temperature. This magnetic phase
diagram is fundamentally similar to that of Takei et al.
mentioned above [13]. Furthermore the magnetic phase
diagram is similar to the one typical for the mixed crystals
of layered antiferromagnetic and ferromagnetic compounds
proposed by de Gennes [18]. Neutron diffraction measure-
ments for CrTe0.6Sb0.4 and CrTe0.4Sb0.6 are now in
progress.
Fig. 7. (a) Temperature dependence of the magnetization s at 10 kOe of
CrTe12xSbx (0#x#0.2). (b) Temperature dependence of the magneti-
zation s at 10 kOe of CrTe12xSbx (0.3#x#0.7).
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