Effect of Partial Substitution of Ga on the Structural and Magnetic Properties of the Ni–Mn–Ga Heusler Alloys

This study explores the impact of Cu and Zn atoms’ alloying on the magnetic and structural features of cubic and tetragonal phase of the Ni 2 Mn 1.125 Ga 0.875 Heusler alloy, using density functional theory. The partial substitution of Ga atoms by Cu and Zn atoms results in a reduction of energy difference between ferromagnetic and ferrimagnetic states of cubic phase, and in an elevation of the energy barrier between cubic and tetragonal phase. The latter observation indirectly implies that there has been a rise in the temperature of the structural transition that was experimentally observed. Within the scope of calculations of exchange interaction parameters from first principles and Monte Carlo simulations of temperature dependences of magnetization, a Т – х phase diagram was constructed. It has been demonstrated that the Curie temperature of the tetragonal phase exhibits a significant reduction compared to that of the cubic phase with an increase in Cu and Zn content due to the growth in inter-sublattice antiferromagnetic interaction between Mn atoms.