Spin orbit driven perpendicular magnetic anisotropy and near half metallic ferromagnetism in HfZCo2 (Z = Al, Ga, In) inverse Heusler alloys for spintronic memory.

The development of multifunctional magnetic materials combining high spin polarization with controllable magnetic anisotropy is essential for next-generation spintronic technologies, particularly for efficient spin injection as well as non-volatile memory applications. Despite extensive research on lighter transition-metal Heuslers, the specific impact of heavy 5d elements on relativistic electronic structure and magnetic anisotropy in inverse Heusler configurations remains less explored. To address this gap, we report comprehensive first-principles study of electronic structure, magnetic behavior and magnetic anisotropy of inverse full-Heusler HfZCo2 alloys using density functional theory with fully relativistic spin-orbit coupling. All compounds are found to be structurally stable in XA phase and exhibit robust ferromagnetic ground states with total magnetic moments close to 1.0µ B per formula unit, consistent with Slater-Pauling rule. Spin-resolved band structures and density of states reveal HfAlCo2 as true half-metallic ferromagnet, while HfGaCo2/HfInCo2 illustrate near-half-metallic behavior with pronounced pseudogaps at the Fermi level. The calculated spin polarization reaches approximately 89.5%, 68.5%, and 57.8% for Z = Al, Ga, and In, respectively. Orbital-resolved analysis shows that magnetism is dominated by Co-3d states, with strong Co-3d to Hf-5d hybridization stabilizing the electronic structure. Magnetic anisotropy calculations further reveal nearly isotropic behavior in HfAlCo2, in-plane magnetic anisotropy in HfGaCo2 and weak perpendicular magnetic anisotropy in HfInCo2, reflecting sensitivity of SOC-induced anisotropy to chemical substitution and electronic structure. These results identify HfZCo2 alloys as theoretically interesting candidates for further investigation in spintronic applications, particularly as potential spin-polarized materials for spin-injection as well as magnetic-anisotropy studies.