Synthesis and magnetic properties of binary boride REB25 compounds

Binary REB25 (RE = Gd, Tb, Dy, Ho, Er) B-12 icosahedral compounds were succ essfully synthesized and magnetic properties were measured. Measurements do wn to 1.8 K revealed that an antiferromagnetic-like transition occurs in Tb B25 at 2.1 K. This transition temperature is almost one order of magnitude lower than that of the transition in the more magnetically dilute TbB50 The structure of TbB25 is refined and, from the differences of structure, the previous conclusion that B-12 icosahedra are indicated to play an important role in the transition of TbB50 is further supported. The other magnetic r are-earth compounds show Curie-Weiss behaviour down to the lowest temperatu res, with values of the effective moment close to that expected for trivale nt rare-earth compounds.