Hexagonal LMn6Sn4Ge2 investigated by neutron diffraction and 119Sn Mössbauer spectroscopy (LÂ =Â Tb, Ho, Lu)

The hexagonal compounds LMn6Sn4Ge2 (L = Tb, Ho, Lu) have been investigated by neutron diffraction and 119Sn Mössbauer spectroscopy. The location of Ge atoms on the 2c site has been confirmed. The TbMn6Sn4Ge2 compound is ferrimagnetic and characterized by an easy-plane magnetisation in the whole 2-300 K temperature range. The magnetic moments at 2 K are μTb = 8.65μB and μMn = 2.36μB. The HoMn6Sn4Ge2 compound is ferrimagnetic and characterized by an easy-plane magnetisation above 130 K and by an easy cone anisotropy below this temperature. The magnetic moments at 2 K are μTb = 9.26μB and μMn = 2.28μB and the angle with respect to the c axis is θc = 51°. The LuMn6Sn4Ge2 compound is helimagnetic in the 2-300 K temperature range with the Mn moment lying in the (0 0 1) plane but around room temperature, it shows some weak lines associated with an antiferromagnetic structure characterized by a doubling of the c axis. The magnetic moment at 2 K is μMn = 2.27μB. Mössbauer spectroscopy indicates that the Mn slab around the 2(d) Sn site is ferromagnetic. Analysis of the results indicates that replacement of Ge for tin changes the anisotropy direction of the L element probably as a result of a change of the sign of the second order CEF parameter. However, the observation of conical anisotropy of Ho also indicates that the fourth order parameter plays a role.