STRUCTURAL AND MAGNETIC-PROPERTIES OF RFE(6)GE(6) (R=Y, GD, TB, ER)

A series of RFe(6)Ge(6) (R=Y, Gd, Tb, Er) compounds have been prepared by arc-melting. Structural studies using x-ray diffraction (XRD) show that all four as-cast alloys belong to the hexagonal P6/mmm space gro up with similar lattice parameters (for YFe6Ge6, a = 5.12 Angstrom and c = 4.07 Angstrom). After annealing at 900 degrees C for two weeks, b oth YFe6Ge6 and TbFe6Ge6 transform into the orthorhombic Cmcm structur e. 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(6)G e(6) structures. Both the room temperature Fe-57 hyperfine held and th e Neel temperature (TN) are largely independent of the rare-earth, bei ng 14.9(1) T and 487 K respectively for YFe6Ge6.