Two-ion magnetocrystalline anisotropy using maximally localized Wannier functions

Using an ab initio tight-binding Hamiltonian based on maximally localized Wannier functions, we investigate the two-ion magnetocrystalline anisotropy in L1₀-type transition metal compounds such as FePt and FeNi. This method can accurately calculate the MAE over the whole bandfilling range. The smaller basis set allows us to efficiently resolve MAE with a very high resolution in reciprocal space. The k-resolved MAE using the force theorem and perturbation theory agree well with each other, both reflecting the aspects of the Fermi surface. We resolve MAE into intra-sublattice and inter-sublattice contributions using both perturbation and scaling procedures, and agreement between them is excellent. Thus this realistic tight-binding method provides an effective approach to describe and analyze MAE. Once the real-space Hamiltonian is constructed, this approach is orders of magnitude faster than the corresponding first principles techniques, but with very similar accuracy.