Quaternary rare-earth sulfides Nd 7 FeInS 13 and Pr 7 CoInS 13

The quaternary rare-earth sulfides Nd7FeInS13 and Pr7CoInS13 were prepared by reactions of the elements at 1050 °C. Single-crystal X-ray diffraction revealed that they adopt a new orthorhombic structure type (space group Pnma, Z =4; a =11.2079(5) A, b =3.9686(2) A, and c =44.1642(18) A for Nd7FeInS13; a =11.2303(6) A, b =3.9876(2) A, and c =44.506(2) A for Pr7CoInS13). The structure contains two types of one-dimensional chains extending along the b-direction: corner-sharing tetrahedra centred by transition-metal atoms (M = Fe, Co), and edge-sharing octahedra centred by In atoms. The RE atoms (RE = Nd, Pr) are coordinated in monocapped or bicapped trigonal prismatic geometry. In terms of these RE-centred trigonal prisms, the structure of Nd7FeInS13 and Pr7CoInS13 can be considered to be built up of fragments of the structures of Y2HfS5 and RE2S3 (β-Cr3C2-type). Magnetic measurements on Pr7CoInS13 indicated paramagnetic behaviour with no transitions down to 2 K.