Designing ferromagnetic polar half-metallic oxide superlattices

By implementing hybrid-improper ferroelectric mechanism, our first-principles-based investigation of La³⁺Ni³⁺(3d⁷)O₃/Ca²⁺Ni⁴⁺(3d⁶)O₃ superlattice showed a ferromagnetic polar ground state with half-metallic phase. The system showed a ferromagnetic Ni-Ni interaction, but the Ni-3d’s are interacting antiferromagnetically with O-2p. Due to the antiferromagnetic Ni-O interaction, we noted a reduced total magnetization in the system. The system emerged to be half-metallic due to unpaired eg electrons in Ni-3d. Further, we examined a series of compounds utilizing the trilinear mode coupling and found the same ferromagnetic polar half-metallic phase as the ground state. In addition, we discussed how the meta-stable phases can offer entirely different properties than that of ground state structure. The LnNiO₃/CaNiO₃ superlattices where Ln denotes La, Nd, Gd, Dy, Tm, and Lu with polar ferromagnetic spin degree of freedom through design could be crucial for memory storage and memory transport.