Neutron diffraction and Mossbauer study of the magnetic structure of HoFe6Sn6

We have used time-of-flight (ToF) neutron powder diffraction, and both ⁵⁷Fe and ¹¹⁹Sn Mossbauer spectroscopy, to study the independent magnetic ordering behavior of the Fe and Ho sublattices in HoFe₆Sn₆. The crystal structure of HoFe₆Sn₆ is orthorhombic (space group Immm). The Fe sublattice orders antiferromagnetically with a Neel temperature of 559(5) K, determined by differential scanning calorimetry. The ToF neutron diffraction patterns obtained at 30 K and 295 K show that the antiferromagnetic ordering of the Fe sublattice is along [100] with a propagation vector q=[010]. The magnetic space group of the Fe sublattice is I_Pm´m´m´ and the Fe magnetic moment at 30 K is 2.31(5) μ_B. This magnetic structure is confirmed by our ¹¹⁹Sn Mossbauer spectra in which 37% of the Sn nuclei experience a substantial transferred hyperfine field from the Fe sublattice while the remaining 63% of the Sn sites show no magnetic splitting, due to the cancellation of transferred hyperfine fields from the Fe neighbors, in full agreement with our Wigner-Seitz cell calculations for each of the eight Sn sites in the HoFe₆Sn ₆ structure. The Ho sublattice orders ferromagnetically at 9(1) K, ToF data obtained at 4 K show that the Ho moments are aligned along [001], i.e. perpendicular to the Fe ordering. The magnetic space group of the Ho sublattice is Im´m´m. The refined Ho magnetic moments at 4 K are 4.4(2) μB and 5.2(2) μB at the 2a and 4h sites, respectively