Interface-induced perpendicular magnetic anisotropy in Co2FeAl/NiFe2O4 superlattice: first-principles study

Abstract

A light element magnetic tunnel junction with perpendicular magnetic anisotropy (PMA) is crucial for the realization of high thermal stability and low critical switching current in next-generation high-density nonvolatile memory. Using first-principles calculations, we investigate the structure and magnetic anisotropy of a Co₂FeAl/NiFe₂O₄ superlattice. It is found that the most energetically favorable configurations for Co₂FeAl(001)/NiFe₂O₄(001) interfaces are when the interface O atoms in NiFe₂O₄ are on top of the interface metal atoms in Co₂FeAl due to the bonding between interface O atoms in NiFe₂O₄ and interface metal atoms in Co₂FeAl. Interestingly, a large PMA of up to 1.07 mJ m⁻² can be obtained at the interface between Co-terminated Co₂FeAl and NiO-terminated NiFe₂O₄ and the interface Co atoms play an important role in establishing the large PMA at the Co₂FeAl/NiFe₂O₄ interface. The d-orbital-resolved magnetic anisotropy energy of interface and surface Co atoms reveals that compared to surface Co, the matrix element differences between d_z² and d_yz as well as d_x²−y² and d_xy orbitals of the interface Co provide large contributions to the PMA of interface Co, which originates mainly from the different electron occupations of d_z², d_yz, d_x²–y² and d_xy orbitals between the interface Co and surface Co due to the bonding between interface Co atoms in Co₂FeAl and interface O atoms in NiFe₂O₄. Our results indicate that the Co₂FeAl/NiFe₂O₄ heterostructures are promising candidates for achieving large interfacial PMA in light element heterostructures.