Narrow Results

Perpendicular magnetic anisotropy in the initial growth of epitaxial in-plane anisotropic Co ultrathin films on the ZnO(002) crystal surface was discovered. The critical thickness of weak spin reorientation transition phenomenon in deposition process from in-plane to out-of-plane magnetic anisotropy is around 2 nm. Ultrathin 1.2 nm Co film was stabilized by post-irradiation of low-energy N ions from the observation of hysteresis loop transforming from an S-shape soft magnetic state to a square hard magnetic state. The addition of N affected the magnetic behavior. The time-dependent nitridization process was observed using Auger electron spectroscopy. Magneto-optical Faraday effect measurements were used to observe the magnetic properties of high-transmission Co/ZnO(002) and Co–N/ZnO(002) surface. A strong polar magneto-optic Faraday effect was dominated in the 2.0–4.0 nm Co/ZnO(002) surfaces. From the N⁺ implantation that reduces the corresponding coercivity, a hexagonal c-axis lattice structure of Co with a preferred perpendicular anisotropy on the ZnO(002) surface may be explained.