Robust Half‐Metallicity and High Curie Temperature in Inverse‐Heusler Ti 2 Co 1− x Ni x In Alloys: A First‐Principles Study

A first‐principles investigation of inverse‐Heusler Ti 2 Co 1− x Ni x In alloys ( x = 0, 0.25, 0.50, 0.75, and 1) is performed to examine the robustness of half‐metallicity under Co → Ni substitution. Spin‐polarized calculations show that the ferromagnetic XA‐type configuration is energetically favored over the investigated nonmagnetic and antiferromagnetic configurations. Negative formation energies, favorable cohesive energies, and elastic stability criteria support the energetic and mechanical viability of these alloys. The lattice parameter increases with Ni content (6.35–6.41 Å), whereas the bulk modulus generally decreases (124–117 GPa), indicating moderate lattice softening. Both GGA and mBJ calculations preserve half‐metallicity across the entire series. The minority‐spin gap exhibits a nonmonotonic composition dependence, reaching a maximum at x = 0.25 (0.589/0.614 eV within GGA/mBJ) before decreasing toward Ti 2 NiIn, consistent with composition‐induced changes in band filling and d–d hybridization. The total magnetic moments follow the Slater–Pauling rule. Curie‐temperature estimates from an empirical moment‐based relation and the mean‐field approximation both peak at x = 0.75; however, they are interpreted comparatively, with MFA values regarded as upper‐bound estimates. These results reveal distinct composition‐dependent optimization of electronic and magnetic properties and provide predictive guidance for future investigations of Ti 2 Co 1− x Ni x In alloys.