Role of oxygen vacancies in the origin of ferromagnetism in Mn‐doped ZnO

The relationship between the oxygen vacancy and ferromagnetism in Mn‐doped ZnO has been studied based on the first‐principles calculations. Three possible charge states of oxygen vacancies, i.e., neutral ( V O 0 ), 1+ ( V O 1+ ) and 2+ ( V O 2+ ) are considered. Results show that the lattice relaxations around oxygen vacancies are large difference under different charge states. It is found that V O 1+ and V O 2+ oxygen vacancies induce ferromagnetism. However, Mn‐doped ZnO system shows ferromagnetism with V O 0 oxygen vacancies in hydrogenated environment, the ferromagnetism is attributed to the interstitial H, which forms a bridge bond and mediates d ‐ d coupling and stabilizes the ferromagnetic state. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)