Crystal structure and magnetic properties of RCu4Be (R = rare earth) compounds

Abstract

We report the synthesis of new alloys of the composition RCu4Be derived by substituting Be for Cu in the well known parent binary RCu5 (R = rare earth) compounds. For R = Nd, Sm, Gd, Tb, Dy, Ho, and Y, the as cast RCu4Be compounds form in the hexagonal CaCu5 type structure. ErCu4Be and TmCu4Be adopt the cubic AuBe5 type symmetry like their parent compounds. The magnetic properties of RCu4Be compounds have been probed by magnetization, electrical resistivity, and heat capacity measured down to 1.8 K. With the exception of TmCu4Be and nonmagnetic YCu4Be the compounds order magnetically with the highest transition temperature of 56 K observed in GdCu4Be. The nature of the magnetic ordering is predominantly ferromagnetic though the corresponding RCu5 compounds are mostly antiferromagnetic with relatively low magnetic ordering temperatures. The thermal variation of the electrical resistivity is in conformity with their metallic nature and reflects the transition into the magnetically ordered state. The evidence for the bulk nature of the magnetic ordering is further elucidated from the heat capacity data which show anomalies at the magnetic transition.