Structure and physical properties of nonstoichiometric rare-earth cadmium antimonides, RECd 1−xSb 2 ( RE=La, Ce, Pr, Nd, Sm)

Abstract

The ternary rare-earth cadmium antimonides RECd 1− x Sb 2 ( RE=La, Ce, Pr, Nd, Sm) were prepared by reaction of the elements at 1000 °C. The presence of Cd defects, previously found for LaCd 0.700(5)Sb 2 and CeCd 0.660(4)Sb 2, has been confirmed by single-crystal X-ray diffraction studies for the isotypic compounds PrCd 0.665(3)Sb 2 ( a = 4.3592 ( 3 ) Å , c = 10.8619 ( 7 ) Å ), NdCd 0.659(3)Sb 2 ( a = 4.3456 ( 4 ) Å , c = 10.8372 ( 9 ) Å ), and SmCd 0.648(3)Sb 2 ( a = 4.3185 ( 4 ) Å , c = 10.7843 ( 11 ) Å ). These compounds adopt the HfCuSi 2-type structure (Pearson symbol tP8, space group P4/ nmm, Z = 2 ). The electrical and magnetic properties of samples with nominal composition RECd 0.7Sb 2 were investigated. All exhibit metallic behaviour, but CeCd 0.7Sb 2 undergoes an abrupt drop in its electrical resistivity below 3 K. LaCd 0.7Sb 2 exhibits temperature-independent Pauli paramagnetism and SmCd 0.7Sb 2 displays van Vleck paramagnetism. The remaining compounds obey the modified Curie–Weiss law at high temperatures. CeCd 0.7Sb 2 undergoes ferromagnetic ordering below 3 K, reaching a saturation magnetization of ∼1.0 μ B, whereas PrCd 0.7Sb 2 and NdCd 0.7Sb 2 remain paramagnetic down to 2 K.