Effect of Mn doping on the structural, optical, and magnetic properties of In2O3 films

(In1−xMnx)2O3 films were grown by radio frequency-magnetron sputtering technique. Effect of Mn doping on the structural, optical, and magnetic properties of films is investigated systematically. The detailed structure analyses suggest that Mn ions substitute for In3+ sites of the In2O3 lattice in the valence of +2 states, and Mn-related secondary phases or clusters as the source of ferromagnetism is safely ruled out. All films show typical room temperature ferromagnetism. The saturation magnetization Ms increases first, and then decreases, while carrier concentration nc decreases monotonically with Mn doping, implying that the ferromagnetism is not directly induced by the mediated carriers. The optical bandgap Eg of films decreases monotonically with the increase of Mn concentration, and there exists a linear functional dependence between Eg and nc2/3, which is consistent with Burstein-Moss shift arguments. It can be concluded that the ferromagnetic order in Mn-doped In2O3 films is intrinsic, arising from Mn atoms substitution for the In sites of In2O3 lattice. The oxygen vacancies play a mediation role on the ferromagnetic couplings between the Mn ions.