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

The authors report new materials R 2 M 3 X 5 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 Eu 2 Ni 3 Si 5 . Magnetism is observed on Ce 2 Ir 3 Ge 5 , Eu 2 M 3 Si 5 (M=Cu, Pd) and U 2 Rh 3 Si 5 . New intermediate valence materials have been obtained in Ce 2 M 3 Si 5 (M=Rh, Ir), with a rather small deviation from the trivalent state of Ce ion. Eu 2 Ni 3 Si 5 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.