High-field soft-x-ray dichroism of a hard ferrimagnet with easy-plane anisotropy

We performed soft x-ray spectroscopic studies of the ferrimagnet ${\mathrm{TbFe}}_{5}{\mathrm{Al}}_{7}$ with strong easy-plane anisotropy in pulsed magnetic fields up to 29 T along with bulk magnetization and magnetostriction measurements. We observed pronounced amplitude changes of x-ray magnetic circular dichroism and x-ray absorption spectra at the field-induced magnetic transition. This microscopically evidences the simultaneous rotation of the Tb $4f$ and Fe $3d$ magnetic moments from a collinear ferrimagnetic order along the [100] axis to a state with the moments close to [010], the other easy-axis direction of the tetragonal lattice in magnetic fields applied along the [100] axis. We determined the magnetic-anisotropy constant of ${\mathrm{TbFe}}_{5}{\mathrm{Al}}_{7}$ by simulating the high-field macro- and microscopic magnetization process using a two-sublattice model.