Emergence of Room-Temperature Perpendicular Magnetic Anisotropy in Metallic NiCo <sub>2</sub>O <sub>4</sub> Thin Film

Room-temperature perpendicular magnetic anisotropy (PMA) is an essential property for devices based on spintronic technology, and is still a great challenge in transition-metal oxide conductors. In this work, we demonstrated the development of the high-quality NiCo2O4 (NCO) films onto MgAl2O4 substrate by precise control over the growth parameters in the pulsed laser deposition process. The characteristics of strong out-of-plane magnetic easy axis, robust anomalous Hall effect, and smaller angle dependence of magnetoresistance in perpendicular direction are observed in metallic NCO films above 300 K. Thus, the obvious room-temperature PMA behavior is supported by these electric transport and magnetic results. This work is further expanded to investigate the valence state, spin and orbital magnetic moment of the NCO film. The Ni2+, Ni3+, Co2+, and Co3+ ions are co-existed, and the orbital magnetic moment of Ni and Co cations are antiparallel with each other in NCO film. As a result, the cation concentration ratio exhibits significant influence upon the magnetism and electric transport. Room-temperature PMA co-existence with metallic behaviors is promising to the multi-function application in spintronics devices.