Electronic structures and magnetisms of the Co₂TiSb_1-xSn_x (x=0, 0.25, 0.5) Heusler alloys: A theoretical study of the shape-memory behavior

The total energy, electronic structures, and magnetisms of the AlCu₂Mn-type Co₂TiSb_1-xSn_x (x=0, 0.25, 0.5) with the different lattice parameter ratios of c/a are studied by using the first-principles calculations. It is found that the phase transformation from the cubic to the tetragonal structure lowers the total energy, indicating that the martensitic phase is more stable and that a phase transition from austenite to martensite may happen at a lower temperature. Thus, a ferromagnetic shape memory effect can be expected to occur in these alloys. The AlCu₂Mn-type Co₂TiSb_1-xSn_x (x=0, 0.25, 0.5) alloys are weak ferrimagnets in the austenitic phase and martensitic phase.