Macroscopic magnetic properties of the HfFe6Ge6-type RFe6X6 (X = Ge or Sn)compounds involving a non-magnetic R metal

The magnetic properties of the HfFe6Ge6-type RFe6Ge6 (R = Sc, Lu, Ti, Zr, K f and Nb) and RFe6Sn6 (R = Sc, Lu and Zr) compounds have been investigated by susceptibility measurements in the 4.2-700 K temperature range and by ma gnetization measurements at 300 K and 4.2 K in fields up to 1.6 T. The germ anides order antiferromagnetically with Neel points situated above 450 K an d show deviation from simple uniaxial antiferromagnetic behavior at low tem perature. The stannides order below about 570 K and are characterized by a small spontaneous magnetization. In both series the ordering temperature is found to slightly increase when increasing the R metal valence. The result s are discussed and related to previously published powder neutron diffract ion and Fe-57 Mossbauer spectroscopy data. (C) 2001 Elsevier Science B.V. A ll rights reserved.