New rare-earth metal germanides with bismuth substitution. Synthesis, structural variations, and magnetism of the RE[BixGe1−x]2 (RE=Y, Pr, Nd, Sm, Gd–Tm, Lu) compounds

Single-crystals of the novel rare-earth metal-bismuth digermanides with idealized formula RE[BixGe1−x]2 (RE=Y, Pr, Nd, Sm, Gd–Tm, Lu; x<0.16(1)) have been obtained using the Bi-flux technique. Their structures have been established by single-crystal X-ray diffraction; they can be divided into three classes, closely related to the ZrSi2 structure with the space group Cmcm (no. 63). The structural relationship and the variations with the type of the rare-earth metal have been explored and discussed. Temperature-dependent magnetization measurements on the single-crystals reveal magnetic behavior, which have been rationalized based on the mean-field theory. At cryogenic temperatures, the localized 4f electrons in most of the compounds exhibit antiferromagnetic ordering, mediated by the conduction electrons via Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange interactions. - Graphical abstract: This paper details the synthesis and the structural characterization of an extended series of rare-earth metal–bismuth–germanides RE[BixGe1−x]2 (RE=Y, Pr–Sm, Gd–Tm, Lu). They crystallize with the same extended symmetry (space group Cmcm), but with three distinct structures, which are closely related. Magnetization measurements show low-temperature antiferromagnetic ordering. RE[BixGe1−x]2 are the first compounds between these elements. Highlights: ► RE[BixGe1−x]2 (RE=rare-earth metal) are the first compounds of the respective elements. ► Their structures are closely related. ► Three structures can be distinguished based on the packing of the REGe6 triangular prisms. ► All compounds show low-temperature antiferromagnetic ordering.