Mat. Res. Bull. Vol. 8, pp. 105-108, 1973. Pergamon Press, Inc. Printed in the United States.

PREPARATION OF FERRIMAGNETIC SnCr2S 4

A. W. Sleight and C. G. Frederick Central Research Department*

E. I. du Pont de Nemours and Company Experimental Station

Wilmington, Delaware 19898

(Received November ZZ, 197Z; Refereed)

ABSTRACT SnCr2S 4 has been prepared for the first time. It is hex- agonal (a = 21.325~ and c : 3.4690~) and ferrimagnetic

(To : ioo

Introduction

An isotypic series of compounds of the type ACr2X 4 have

been reported (1,2) where A can be Pb, Sr, Ba, or E~ and X can be

S or Se. These compounds have an unknown hexagonal structure and

are generally ferrimagnetic and semiconducting. We have prepared

a phase in the Sn/Cr/S system and found thst it is isotypic with

this series.

Experimental

All reactants had listed purities of 99.9% or better.

Appropriate quantities of the elements were sealed in evacuated

silica ampoules. These were then heated at 800°C for i0 hours.

X-ray powder patterns were obtained at 25°C using a

H~'gg-Guinier camera with CuKc I radiation and an internal standard

of KCI (a = 6.29310A at 25°C). Cell dimensions were refined by

*Contribution No. 1972.

105

106 FERRIMAGNETIC SnCrzS 4 Vol. 8, No. I

least squares. Magnetization data were obtained from 4.2 to

298 K on a vibrating sample magnetometer.

Results

The cell dimensions of SnCr2S 4 are given in Table i

where they are compared to the cell dimensions of some known iso-

typic compounds. SnCr2S 4 is black with a fibrous crystal habit

which is typical of the isotypic series (2). An impurity of SnS

was identified, and it could not be completely separated from the

fibers of "SnCr2S4".

TABLE I

Cell Dimensions and Curie Temperatures

Compound a, ~ c, ~ Tc, K

SnCr2S 4 21.325 3.4690 lO0

PbCr2S 4 21.410 3.4755 121 (21.411) * (3.478) (138)

PbCr2Se 4 22.342 3.5946 198 (22.327) (3.648) (194)

EuCr2Se 4 22.354 3.6357 140 22.414 3.6285 (22.380) (3.627) (155)

*Values in parentheses are from Reference 2.

SnCr2S 4 is ferrlmagnetlc with a moment of lO emu/gm

when extrapolated to 0 K and infinite field. Of course, the true

moment will be slightly higher since our sample contained a very

small amount of diamagnetic SnS. The Curie temperature of

SnCr2S 4 is compared to that of some Isotyplc compounds in Table I,

The fibers of SnCr2S 4 were too small for reliable four-

probe electrical measurements. An attempt at a two-probe elec-

trical measurement indicated a resistivity of about l05 ohm-cm

at 25°C.

Vol. 8, No. i FERRIMAGNETIC SnCrzS 4 107

Some known compounds isotypic with SnCr2S 4 were pre-

pared in the course of this work. Their cell dimensions and

Curie temperatures are also given in Table i.

Discussion

SnCr2S 4 is ferrimagnetic and apparently semiconducting.

Characterization is difficult because large crystals and pure

samples have not been prepared. This has also been a problem

for the other members of this isotypic series. Unfortunately,

the structure is not known for this series. Furthermore, the com-

position is not known for certain for any member of this series,

but it is close to ACr2X 4 (2). The composition for at least some

members is variable. This is shown, for example, by the varia-

tion in cell dimensions (Table i) from preparation to preparation.

Further discussion of compounds of this type should await struc-

ture and composition determinations.

Acknowledgment

The electrical resistivity was measured by J. L.

Gillson.

References

i. ~. P. F. A. M. Omloo and F. Jellinek, Recuell Trav. Chim.

Pays-Has 87, 545 (1968).

2. W. P. F. A. M. Omloo, J. C. Bommerson, H. H. Heikens, H. Risselada, M. B. Vellinga, C. F. van Bruggen, C. Haas, and F. Jellinek, Phys. Stat. Sol. 5A, 349 (1971).