Covalent magnetism in the RFe 6Ge 6 series

The electronic structure of the RFe ₆ Ge ₆ compounds ( R = Sc, Lu, Ti, Zr, Hf and Nb) of HfFe ₆ Ge ₆ -type structure has been studied using the muffin-tin Korringa-Kohn-Rostoker method in a non-relativistic approach. The chemical bonding is analyzed based on the l-decomposed site projected densities of states. Spin-dependent changes in the R nd- Fe 3d covalent bond are shown to be responsible for the experimentally observed rise in the Fe moment and hyperfine field upon increasing the R valency. The limited quantitative agreement between theoretical and experimental values is interpreted as being due to a non-negligible orbital moment and to a significant asphericity in the spin density at the iron site. The theoretical results also forecast a strong increase of the Ge(2e) transferred hyperfine field with the R valency. Received 20 December 2002 Published online 4 June 2003 RID="a" ID="a"e-mail: Thomas.Mazet@lcsm.uhp-nancy.fr RID="b" ID="b"Associé au CNRS (UMR 7555)