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

The Feeble Role of Oxygen Vacancies in Magnetic Coupling in ZnO Based Dilute Magnetic Semiconductors. M.H.N.Assadi, Y.B.Zhang, S.Li: Journal of Physics - Condensed Matter, 2010, 22[48], 486003