First-principles calculations of enhanced ferromagnetism in ZnO codoped with cobalt and nitrogen

Using first-principles calculations based on density functional theory, N-codoped ZnO:Co has been demonstrated to be potentially a $p$-type diluted magnetic semiconductor. By investigating 13 geometrically distinct configurations, Co and N dopants are found to have a tendency toward staying close to each other with most stable –O–Co–N–Co–O– complexes. The dominant ferromagnetic interaction is due to the hybridization between N $2p$ and Co $3d$ states, which is strong enough to lead to hole-mediated ferromagnetism at room temperature. The ferromagnetic coupling strongly relies on the distance of N from Co, while it weakly depends on the direction of aligned Co ions.