Magnetic properties of RMn 6Sn 6 (R=Gd–Er) compounds from neutron diffraction and Mössbauer measurements

Abstract

The magnetic structures of the HfFe 6Ge 6-type structure RMn 6Sn 6 (R=Gd–Er) compounds have been investigated by neutron diffraction and 155 Gd and 166 Er Mössbauer spectroscopy. Strong Mn-R antiferromagnetic coupling causes the rare earth and manganese sublattices to order simultaneously, yielding collinear ferrimagnetic arrangements in the whole ordered state for R=Gd, Tb, Dy, Ho compounds and below 75 K in ErMn 6Sn 6. Neutron diffraction studies of Tb- and DyMn 6Sn 6 above room temperature and in the whole ordered state of GdMn 6Sn 6 prove the planar anisotropy of the Mn sublattice whereas the rare-earth anisotropy for R elements with negative α 2 Stevens factor yields total (Tb) or partial (Dy, Ho) spin reorientation processes of both R and Mn sublattices at low temperature. Mössbauer spectroscopy shows that the rare earth single ion anisotropy is related to an interplay of the second- and fourth-order crystal electric field coefficients.