A study of the crystal structure of a Tb-Dy-Fe alloy during annealing via rietveld analysis

The crystal structure and magnetic structure of Tb-Dy-Fe compounds before and after annealing heat treatment were researched, in order to further study the influence factors on the magnetic performance besides the orientation and phases. The Rietveld method was used to refine the structural data and obtain small changes in the structure. The results confirm the existence of tetragonal and rhombohedral phases at room temperature, which is consistent with previous findings. Both samples had tetragonal structures and rhombohedral distortion structures at room temperature. The lattice constants of the rhombohedral structure were a = 5.18160 Å and c = 12.72178 Å, while the volume diagonal of the tetragonal cell was 12.69513 Å, indicating the amount of change between the two structures. The volume proportion of the hexagonal phase increased from 25% to 51% after heat treatment. The refinements made on the basis of the neutron patterns indicated that the refined Tb/Dy and Fe moments are antiparallel, while the average atomic magnetic moment of Tb/Dy increased in the annealed state compared with that in the as-cast state. By combining all the analytical results, we discussed the effect of structural distortion on the magnetostriction of Tb-Dy-Fe.