Crystal structure, 57Fe Mössbauer spectroscopy and magnetization of UxFe6Sn6 (0≤x≤0.6)

The UxFe6Sn6 (0≤x≤0.6) intermetallics were prepared as polycrystalline samples by arc melting followed by annealing. They crystallize in the P6/mmm space group as a lacunary variant of the HfFe6Ge6-type, with an ordered insertion of U within the Sn8 voids of the FeSn framework, and are isostructural with the RxFe6Sn6 compounds (R=Sc, Zr, Tm, Yb, Lu). 57Fe Mössbauer spectroscopy shows that the Fe magnetic moments, μFe, are already ordered at room temperature. Anisotropic contributions to the total hyperfine field at the Fe site indicates that μFe are perpendicular to the crystallographic c axis in contrast to the Sc, Zr and rare-earth (except Yb) containing compounds, where μFe are directed along the c axis. The values deduced for the angles between the main axes of the electric field gradient and μFe further show that, within each (001) plane, μFe have a ferromagnetic arrangement similar to that in FeSn and Yb0.6Fe6Sn6. In UxFe6Sn6, the hyperfine fields increase with U content. Magnetization data in the 2–300 K show small ferromagnetic components for the U0.4Fe6Sn6 and U0.6Fe6Sn6 compositions.