MAGNETIC AND THERMAL-PROPERTIES OF THE MIXED-VALENCE COMPOUNDS SM2S3, SM3S4, AND SM3SE4

The magnetization and low temperature specific heat of small (20 mg) single crystals of Sm2S3, Sm3S4 and Sm3Se4 have been measured to test the crystal field model for Sm3+ in the Th3P4 structure suggested earlier for the compounds EuSm2S4 and SrSm 2S4. In this model, the Γ8 quartet is lowest but split (by ∼2.4 K) by a small noncubic crystal field. A pronounced upturn in the specific heat below 7 K is predicted. The present measurements down to 1.5 K confirm this prediction for every compound measured, the same feature occurring at almost precisely the same temperature. In addition, a comparison of the experimental susceptibilities of Sm2S3 and Sm3S4 indicates that simple addition of the contributions of the different ionic species (Sm2+ and Sm 3+) is sufficient to explain the magnetic behavior of these mixed valent Sm compounds.