First-principles and Monte Carlo studies of the Fe2NiZ compounds on exchange interactions and Curie temperatures

Using the spin-polarized relativistic Korringa-Kohn-Rostoker in combination with Monte Carlo calculations, we study the exchange interactions and Curie temperatures of Fe2NiZ (Z = Al, Ga, In, Si, Ge, Sn, P, As, Sb) compounds with the Hg2CuTi structure. Results show that the inter-sublattice Fe(A)-Fe(B) exchange plays a dominant role in interactions, and provide a major contribution to the Curie temperature. In the same period, the inter-sublattices Fe(A)-Fe(B) along with Fe(B)-Ni(C) and Fe(A)-Ni(C) interactions decrease when changing Z from III to V group. In contrast, the intra-sublattice Fe(B)-Fe(B) exchange exhibits an upward tendency, and the intra-sublattice Ni(C)-Ni(C) interaction almost closes to zero in all cases. Further, the Curie temperature is estimated based on the Heisenberg exchange coupling parameters between the constituents. The calculated Curie temperatures noticeably higher than the room temperature indicate these compounds more favorable in realistic spintronics application. In addition, the Monte Carlo method is adopted to obtain more accurate Curie temperatures by modeling the normalized magnetization as functions of the temperature, our results are in good accordance with available experimental values.