The feeble role of oxygen vacancies in magnetic coupling in ZnO based dilute magnetic semiconductors.

The role of the oxygen vacancy (V(O)) as the dominant defect in ZnO in magnetic interactions of ZnO based dilute magnetic semiconductors (DMSs) was examined in detail using density functional theory. It was found that V(O) does not lead to a thermally activated carrier mediated magnetism or form magnetic centers in the ZnO lattice. However, neutral V(O) may facilitate the ferromagnetism, but has a limited influence on the original antiferromagnetic coupling of the magnetic ions in oxygen stoichiometric ZnO DMSs. As a result, the ferromagnetism observed in previous experiments should be attributed to other defects such as hydrogen contamination or zinc interstitials.