Magnetic and Transport Properties of RESnxSb2 (RE=La, Ce, Pr, Nd, Sm; x=0.5, 0.7)

The nonstoichiometric rare-earth tin antimonides RESnxSb2 (RE=La, Ce, Pr, Nd, Sm) were characterized by 119Sn M?ssbauer spectroscopy and their transport and magnetic properties were measured. The presence of nearly zero-valent Sn is suggested by the similarity of the 119Sn M?ssbauer parameters in LaSnxSb2 (0.1< or =x< or = 0.7) to those of elemental beta-Sn. All RESn0.7Sb2 compounds exhibit metallic behavior. CeSn0.7Sb2 and NdSn0.7Sb2 show drops in resistivity below 8 K; this is attributed to a transition to a magnetically ordered state. At 25 K, CeSn0.7Sb2 also displays a resistivity minimum characteristic of ordered Kondo lattices. Magnetic studies indicate that, below 4 K, CeSnxSb2 (x=0.5, 0.7) orders ferromagnetically, whereas NdSnxSb2 (x=0.5, 0.7) orders antiferromagnetically and undergoes a metamagnetic transition at HC=5.5 T and 2 K. Neither PrSnxSb2 nor SmSnxSb2 (x=0.5, 0.7) displays long-range magnetic ordering above 2 K.