Structural and magnetic properties in the polymorphs of CeRh_0.5Ge_1.5

Abstract

We investigate the structural and magnetic properties in the polymorphs of a new compound CeRh_0.5Ge_1.5. Depending upon the starting materials, and the slightly different synthesis method, we find that CeRh_0.5Ge_1.5 compound exists in two different space groups. The first compound, α-CeRh_0.5Ge_1.5 crystallizes in tetragonal α-this₂ structure type in space group I4₁/amd with lattice parameters, a=4.2034(6) Å and c=14.770(3) Å. In this structure, the cerium atoms occupy the position between the Rh/Ge tetrahedral layers. On the other hand, the second compound, namely β-CeRh_0.5Ge_1.5 crystallizes in the AlB₂ type hexagonal structure in space group P6/mmm, with lattice parameters, a=4.2615(7) Å and c=4.1813(9) Å. The crystal structure of β-CeRh_0.5Ge_1.5 consists of two dimensional Rh/Ge hexagonal units and the cerium atoms are sandwiched between them. Magnetization studies exhibit magnetic ordering, as evident from a sharp peak in the plot of magnetic susceptibility measured as a function of temperature in a fixed magnetic field, in α-CeRh_0.5Ge_1.5 and β-CeRh_0.5Ge_1.5 at 3.6 K and 12 K, respectively. Structural and magnetic properties of both compounds are presented and discussed here.