Crystallographic and magnetic properties of HfFe6Ge6-type REFe6Sn4Ge2 compounds (REÂ =Â Y, Gd-Er)

The REFe6Sn4Ge2 (RE = Y, Gd-Er) compounds have been synthesized and studied by powder X-ray diffraction and magnetisation measurements. These compounds crystallize in the hexagonal HfFe6Ge6 structure although the parent ternary compounds REFe6X6 (X = Ge, Sn) display more complicated orthorhombic crystal structure. This evolution is discussed and interpreted on the basis of the relaxation of some RE-X contacts in the quaternary compounds. The iron sublattice order antiferromagnetically above room temperature (554 ≤ TN ≤ 560 K) while the paramagnetic RE compounds display a second transition at low temperature (7.3 ≤ Tt ≤ 42.7 K). The magnetisation versus field curves display a metamagnetic behaviour at 4.2 K. The corresponding value of the magnetisation suggests a non-collinear ordering of the RE sublattice.