The structural and magnetic properties of Fe_2−xNiGa_1+x Heusler alloys

The structural and magnetic properties of Fe_2−xNiGa_1+x (x=0~1) Heusler alloys have been investigated by experimental observation and calculation. In this system, a structural transition is found as a function of composition. A higher Ga content leads to an atomic-order transformation from Hg₂CuTi to B2. The magnetization decreases due to the dilution effect and the competition between the magnetic interactions and enhanced covalent bonding. The calculation of electronic structure indicates that adding Ga enhances the p–d orbital hybridization between the transition-metal and main-group-element atoms at nearest-neighbor distance. A magnetic and a structural phase diagram have been obtained in which the composition dependences of the lattice constant, the ordering temperature and the Curie temperature show cusps at a critical composition of x=0.32