Magnetic ordering in the HfFe6Ge6-type TbFe6Sn4Ge2 compound

We have determined the magnetic structures of the Tb and Fe sublattices in TbFe6 Sn4 Ge2 by combining powder neutron diffraction with Fe57 and Sn119 Mössbauer spectroscopy. TbFe6 Sn4 Ge2 adopts the hexagonal HfFe6 Ge6-type (P6/mmm) crystal structure. The Fe sublattice orders antiferromagnetically below TN=518(3)  K, with the moments parallel to c. At Tt=42(1)  K, the Tb sublattice orders helimagnetically, with a propagation vector Q=(0,0,0.0963) r.l.u. (at 2 K). This imposes helimagnetic order (with an identical propagation vector) on the Fe sublattice, indicating that the two sublattices are coupled for T