Subtle interplay between native point defects and magnetism in ZnO:Co

Distribution of Co ions and its effect on magnetic properties of ZnO:Co in the presence of native point defects, oxygen vacancy, and interstitial hydrogen, have been investigated using first-principles density functional calculations. The study provides a fundamental theoretical understanding on the correlation between magnetism and the distribution of magnetic ions and the native point defects in the semiconducting host. Results show that Co ions have a strong tendency toward aggregation via oxygen within $ab$ plane in the presence of point defects. The room temperature ferromagnetism observed experimentally in ZnO:Co is mainly dominated by the interstitial hydrogen rather than oxygen vacancy.