Local chemical and magnetic disorder within the HfFe6Ge6-type RFe6Sn6 compounds (R = Sc, Tm, Lu and Zr)

Microprobe analysis, neutron diffraction experiments and Fe-57 Mossbauer measurements have been performed on powder samples of the ternary HfFe6Ge6-type RFe6Sn6 intermetallics (R =Sc,Tm,Lu) and on the new ZrFe6Sn6 compound. Both microprobe analysis and neutron diffraction indicate an under-stoichiometry in R elements (approximate to 10%). According to neutron diffraction study, the magnetic structures always consist of ferromagnetic easy-axis (0 0 1) Fe planes antiferromagnetically stacked along the c-axis (+ - + -) with mu(Fe) close to 2.3 mu(B) at 2K. The Fe-57 Mossbauer spectroscopy reveals that a fraction gamma of iron atoms, roughly proportional to the above mentioned under-stoichiometry, have moments which deviate from the c-axis. These observations are discussed in relation to the easy-plane magnetic arrangement adopted by the FeSn parent compound. (C) 2000 Elsevier Science B.V. All rights reserved.