Crystallographic data and magnetic properties of new RTX compounds (RLa-Sm, Gd; TRu, Os; XSi, Ge). Magnetic structure of NdRuSi

Abstract

Investigations made by powder X-ray diffraction, susceptibility measurements and neutron diffraction experiments on new ternary silicides RRuSi (RLa-Sm, Gd), germanides RRuGe (RLa-Sm) and CeOsSi are reported. All these new compounds crystallize in the well-known tetragonal structure of the CeFeSi type (space group P4/ nmm). This structure, which is closely related to the ThCr 2Si 2- and TbFeSi 2-type structures, can be described as isolated “ThCr 2Si 2 blocks” (BaAl 4 slab) connected via R-R contacts. LaRuSi and LaRuGe are Pauli paramagnets, while CeRuSi, CeRuGe and CeOsSi are Curie-Weiss paramagnets down to 4.2 K with effective moments of 2.56, 2.55 and 2.03 μ B respectively. GdRuSi and the Sm silicide and germanide behave ferromagnetically below 85, 65 and 45 K respectively, whereas the Pr and Nd compounds are antiferromagnetic with Néel temperatures of about 74 K (Si) and about 64 K (Ge). Neutron diffraction experiments show that NdRuSi has a collinear antiferromagnetic structure which consists of ferromagnetic (001) Nd layers (with moments perpendicular to the layers) antiferromagnetically coupled along the c axis in the sequence + − − + ( μ Nd = 2.81(5) μ B). The results are discussed and compared with those obtained on the closely related RRu 2Si 2 and isotypic RFeSi and RCoGe compounds.