Structural and magnetic properties of RFe/sub 6/Ge/sub 6/ (R=Y, Gd, Tb, Er)

A series of RFe/sub 6/Ge/sub 6/ (B=Y, Gd, Tb, Er) compounds have been prepared by arc-melting. Structural studies using X-ray diffraction (XBD) show that all four as-cast alloys belong to the hexagonal P6/mmm space group with similar lattice parameters (for YFe/sub 6/Ge/sub 6/, a=5.12 /spl Aring/ and c=4.07 /spl Aring/). After annealing at 900/spl deg/C for two weeks, both YFe/sub 6/Ge/sub 6/ and TbFe/sub 6/Ge/sub 6/ transform into the orthorhombic Cmcm structure. Mossbauer spectroscopy and magnetisation measurements show that all of the alloys are antiferromagnetically ordered at room temperature. We find a single Fe crystallographic site, consistent with the RFe/sub 6/Ge/sub 6/ structures. Both the room temperature /sup 57/Fe hyperfine field and the Neel temperature (T/sub N/) are largely independent of the rare-earth, being 14.9(1) T and 487 K respectively for YFe/sub 6/Ge/sub 6/.>