Abstract:
This paper studies the parameters of the magnetic exchange interaction $J_{ij}$ for the crystal structures of D0$_3$ and L1$_2$ Fe$_{75}$Ga$_{25}$ alloys using the Hamiltonian based on Wannier functions and the density functional theory. The largest ferromagnetic interaction in the first coordination sphere for the L1$_2$ phase was 18 meV, which is 3 meV less than the results obtained using Green's function method. In the D0$_3$ phase the largest ferromagnetic interaction in the first coordination sphere is observed between atoms of different iron sublattices. The difference from the results obtained previously using the Korringa-Kohn-Rostoker method is approximately 10 meV. Using the values of the magnetic exchange parameters, the Curie temperature was calculated in a Monte Carlo simulation. For the L1$_2$ structure, the Curie temperature was estimated to be 1007 K, which is in good agreement with experimental data. However, for the D0$_3$ structure, the estimated Curie temperature of 517 K is lower than the experimental value by about 200 K.
Keywords:Fe-based alloys, first principles calculations, Wannier functions, magnetic exchange parameters, Curie temperature.
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