Mechanism of ferromagnetism in nitrogen-doped ZnO: First-principle calculations

Based on our first-principle calculations, ZnO doped by a nonmagnetic $2p$ light element (N) is predicted to be ferromagnetic. The local magnetic moments that are mainly localized on doped N atoms introduced total moments of 1.0μB/atom. The long-range magnetic coupling of N-doped ZnO can be attributed to a p-d exchange-like p-p coupling interaction involving holes, which is derived from the similar symmetry and wave function between the impurity (p-like t₂) and valence $(p)$ states. We also propose a codoping mechanism, using beryllium and nitrogen as dopants in ZnO, to enhance the ferromagnetic coupling and to increase the solubility and activity.