Preparation of ferrimagnetic SnCr2S4

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<ul><li><p>Mat. Res. Bull. Vol. 8, pp. 105-108, 1973. Pergamon Press, Inc. Printed in the United States. </p><p>PREPARATION OF FERRIMAGNETIC SnCr2S 4 </p><p>A. W. Sleight and C. G. Frederick Central Research Department* </p><p>E. I. du Pont de Nemours and Company Experimental Station </p><p>Wilmington, Delaware 19898 </p><p>(Received November ZZ, 197Z; Refereed) </p><p>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 </p><p>Introduction </p><p>An isotypic series of compounds of the type ACr2X 4 have </p><p>been reported (1,2) where A can be Pb, Sr, Ba, or E~ and X can be </p><p>S or Se. These compounds have an unknown hexagonal structure and </p><p>are generally ferrimagnetic and semiconducting. We have prepared </p><p>a phase in the Sn/Cr/S system and found thst it is isotypic with </p><p>this series. </p><p>Experimental </p><p>All reactants had listed purities of 99.9% or better. </p><p>Appropriate quantities of the elements were sealed in evacuated </p><p>silica ampoules. These were then heated at 800C for i0 hours. </p><p>X-ray powder patterns were obtained at 25C using a </p><p>H~'gg-Guinier camera with CuKc I radiation and an internal standard </p><p>of KCI (a = 6.29310A at 25C). Cell dimensions were refined by </p><p>*Contribution No. 1972. </p><p>105 </p></li><li><p>106 FERRIMAGNETIC SnCrzS 4 Vol. 8, No. I </p><p>least squares. Magnetization data were obtained from 4.2 to </p><p>298 K on a vibrating sample magnetometer. </p><p>Results </p><p>The cell dimensions of SnCr2S 4 are given in Table i </p><p>where they are compared to the cell dimensions of some known iso- </p><p>typic compounds. SnCr2S 4 is black with a fibrous crystal habit </p><p>which is typical of the isotypic series (2). An impurity of SnS </p><p>was identified, and it could not be completely separated from the </p><p>fibers of "SnCr2S4". </p><p>TABLE I </p><p>Cell Dimensions and Curie Temperatures </p><p>Compound a, ~ c, ~ Tc, K </p><p>SnCr2S 4 21.325 3.4690 lO0 </p><p>PbCr2S 4 21.410 3.4755 121 (21.411) * (3.478) (138) </p><p>PbCr2Se 4 22.342 3.5946 198 (22.327) (3.648) (194) </p><p>EuCr2Se 4 22.354 3.6357 140 22.414 3.6285 </p><p>(22.380) (3.627) (155) </p><p>*Values in parentheses are from Reference 2. </p><p>SnCr2S 4 is ferrlmagnetlc with a moment of lO emu/gm </p><p>when extrapolated to 0 K and infinite field. Of course, the true </p><p>moment will be slightly higher since our sample contained a very </p><p>small amount of diamagnetic SnS. The Curie temperature of </p><p>SnCr2S 4 is compared to that of some Isotyplc compounds in Table I, </p><p>The fibers of SnCr2S 4 were too small for reliable four- </p><p>probe electrical measurements. An attempt at a two-probe elec- </p><p>trical measurement indicated a resistivity of about l05 ohm-cm </p><p>at 25C. </p></li><li><p>Vol. 8, No. i FERRIMAGNETIC SnCrzS 4 107 </p><p>Some known compounds isotypic with SnCr2S 4 were pre- </p><p>pared in the course of this work. Their cell dimensions and </p><p>Curie temperatures are also given in Table i. </p><p>Discussion </p><p>SnCr2S 4 is ferrimagnetic and apparently semiconducting. </p><p>Characterization is difficult because large crystals and pure </p><p>samples have not been prepared. This has also been a problem </p><p>for the other members of this isotypic series. Unfortunately, </p><p>the structure is not known for this series. Furthermore, the com- </p><p>position is not known for certain for any member of this series, </p><p>but it is close to ACr2X 4 (2). The composition for at least some </p><p>members is variable. This is shown, for example, by the varia- </p><p>tion in cell dimensions (Table i) from preparation to preparation. </p><p>Further discussion of compounds of this type should await struc- </p><p>ture and composition determinations. </p><p>Acknowledgment </p><p>The electrical resistivity was measured by J. L. </p><p>Gillson. </p><p>References </p><p>i. ~. P. F. A. M. Omloo and F. Jellinek, Recuell Trav. Chim. Pays-Has 87, 545 (1968). </p><p>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). </p></li></ul>