Roles of Cu codoping and oxygen vacancies on ferromagnetism in In₂O₃:Fe

The electronic structures and the ferromagnetic (FM) stability in In₂O₃:Fe (IFO) with additional Cu and oxygen vacancy (V_O) doping have been investigated using first-principles calculations within the framework of density-functional theory. It is found that pure IFO has an antiferromagnetic ground state, but the existence of V_O or with Cu codoping could lead to a weak FM coupling in IFO system for some special configurations. The stability of the ferromagnetism is greatly enhanced by the coexistence of V_O and Cu codoping in IFO system. We demonstrate that the role of Cu ions is to act as superexchange mediators causing an indirect FM coupling between Fe cations through the hybridization of the Cu 3d states with the O 2p states. The delocalized hybridization consisted of Fe 3d, O 2p, and Cu 3d is found to be very efficient to mediate the FM exchange interaction. In favor of the FM state, Cu ions prefer to locate adjacent to the Fe ions in order to form Fe1-O1-Cu-O2-Fe2 coupling chain. The results of our calculations suggest the possibility of fabricating In₂O₃ based transparent spintronics by (Fe, Cu) codoping in a reduced growth ambient.