preparation of ferrimagnetic sncr2s4

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  • 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 : i oo

    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 800C for i0 hours.

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

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

    of KCI (a = 6.29310A at 25C). 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 25C.

  • 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).

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