Interface-induced perpendicular magnetic anisotropy in Co2FeAl/NiFe2O4 superlattice: First-principles study
A light element magnetic tunnel junction with perpendicular magnetic anisotropy (PMA) is crucial for realization of high thermal stability and low critical switching current in the next-generation high-density nonvolatile memory. Using first-principles calculations, we investigate the structure and magnetic anisotropy of 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/m2 can be obtained at the interface between Co-terminated Co2FeAl and NiO-terminated NiFe2O4 and the interface Co atoms play an important role for establishing the large PMA at Co2FeAl/NiFe2O4 interface. The d-orbital-resolved magnetic anisotropy energy of interface and surface Co atoms reveal that compared to surface Co, the matrix element differences between dz2 and dyz as well as dx2–y2 and dxy orbitals of the interface Co provide the large contributions to the PMA of interface Co, which originates mainly from the different electron occupations of dz2, dyz, dx2–y2 and dxy orbitals between the interface Co and surface Co due to the bonding between interface Co atoms in Co2FeAl and interface O atoms in the NiFe2O4. Our results indicate that the Co2FeAl/NiFe2O4 heterostructures are promising candidates for achieving large interfacial PMA in light element heterostructures.