Enhanced Curie temperature in atomically thin perpendicular magnetic anisotropic oxide film through interfacial engineering

Abstract

The inverse spinel oxide NiCo2O4, known for its high Curie temperature, low resistivity, and perpendicular magnetic anisotropy, is a promising candidate for the development of next-generation spintronic devices. However, reducing the thickness of the NiCo2O4 film to a few atomic layers degrades its room temperature magnetic and electrical properties, limiting its practical application. In this study, a Co3O4 buffer layer is introduced into ultrathin NiCo2O4 films, which significantly enhances the Curie temperature beyond room temperature and reduces the resistivity, while preserving the strong perpendicular magnetic anisotropy as well as the robust anomalous Hall effect. It is found that the sheet resistance dramatically decreases with the increase in Co3O4 thickness. The observed phenomena may originate from the increased occupation of Ni3+ ions at octahedral sites due to the interfacial coupling, resulting in the intrinsic linear relationship between resistivity and Curie temperature. Additionally, the scaling relation between the anomalous Hall conductivity and longitudinal conductivity highlights the complex interaction between spin-dependent impurity scattering and the band intrinsic Berry curvature. This study indicates that interfacial coupling is an effective strategy for tuning the physical properties of oxides, providing a promising avenue for the application of NiCo2O4-based materials in miniaturized spintronic devices.