Neutron diffraction and 57Fe Mِssbauer study of the HfFe6Ge6-type RFe6Ge6 compounds (R=Sc, Ti, Zr, Hf, Nb)

Both neutron diffraction experiments and 57Fe Mössbauer 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 antiferromagnetic stacking along the c-axis of ferromagnetic (001) Fe planes, the easy-direction of magnetization being along [001]. However, for R=Ti, Zr and Nb, we observe that, at 4.2 K, ≈30% of iron atoms have moments which deviate from the c-axis. Both the ordered magnetic moment and the hyperfine field on iron atoms are found to increase with the R valency. This observation is tentatively attributed to an increase of the hybridization of the d valence states of the R metal with the 3d iron states.