Magnetism and mixed valence in some R₂M₃X₅ compounds: R = Ce, Eu, U; M = d metals, X = Si, Ge

Abstract

The authors report new materials R₂M₃X₅ compounds mainly based on possible anomalous rare earths: Ce, Eu and actinide U. Lattice parameters, susceptibility and L_III absorption edge versus temperature measurements have been performed on Ce, Eu based materials. Mossbauer experiments versus temperature are also reported on Eu₂Ni₃Si₅. Magnetism is observed on Ce₂Ir₃Ge₅, Eu₂M₃Si₅ (M=Cu, Pd) and U₂Rh₃Si₅. New intermediate valence materials have been obtained in Ce₂M₃Si₅ (M=Rh, Ir), with a rather small deviation from the trivalent state of Ce ion. Eu₂Ni₃Si₅ is an intermediate valence compound. From Isomer Shift measurements and L_III absorption edge measurements versus temperature the valence of Eu changes from #2.6 at 300K to #2.7 at 4.2K.