Magnetic interactions between native defects in ZnO: A first-principles study

Based on first-principles density-functional calculations, we investigate the magnetic interactions between the native point defects in ZnO. In our lattice models, the ferromagnetic interactions, which are stable at room temperature, are effective within the third nearest-neighbor distance of neutral Zn vacancies in the direction of a-axis, while they occur only between nearest-neighboring Zn vacancies in the direction of c-axis. On the other hand, no magnetic couplings are found between spin-polarized O antisites that are in the 1-charge state. An estimate using the hardspheroid approximation indicates that room-temperature ferromagnetism in ZnO can be induced by Zn vacancies of a few percent.