Magnetic exchange parameters and the Curie temperature of Fe75Ga25 alloy

This paper studies the parameters of the magnetic exchange interaction Jij for the crystal structures of D03 and L12 Fe75Ga25 alloys using the Hamiltonian based on Wannier functions and the density functional theory. The largest ferromagnetic interaction in the first coordination sphere for the L12 phase was 18 meV, which is 3 meV less than the results obtained using Green's function method. In the D03 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 L12 structure, the Curie temperature was estimated to be 1007 K, which is in good agreement with experimental data. However, for the D03 structure, the estimated Curie temperature of 517 K is lower than the experimental value by about 200 K.