Neutron diffraction and Fe-57 Mossbauer study of the HfFe6Ge6-type RFe6Ge6compounds (R = Sc, Ti, Zr, Hf, Nb)

Both neutron diffraction experiments and Fe-57 Mossbauer measurements have been performed on powder samples of the HfFe6Ge6-type RFe6Ge6 compounds (R = Sc, Ti, Zr, Hf, Nb). These compounds are characterized by an antiferromag netic stacking along the c-axis of ferromagnetic (001) Fe planes, the easy- direction of magnetization being along [001]. However, for R = Ti, Zr and N b, we observe that, at 4.2 K, approximate to 30% of iron atoms have moments which deviate from the c-axis. Both the ordered magnetic moment and the hy perfine held on iron atoms are found to increase with the R valency. This o bservation is tentatively attributed to an increase of the hybridization of the d valence states of the R metal with the 3d iron states. (C) 2000 Else vier Science Ltd. All rights reserved.