Ferromagnetism in ZnO codoped with transition metals: Zn1-x(FeCo)(x)O and Zn1-x(FeCu)(x)O

We have investigated electronic structures and magnetic properties of ZnO-based potential diluted magnetic semiconductors codoped with transition metals: Zn1-x(FeCo)(x)O and Zn1-x(FeCu)(x)O. We have found that the origin of the observed ferromagnetism in Zn1-x(FeCo)(x)O would be different from that in Zn1-x(FeCu)(x)O. Zn1-x(FeCo)(x)O does not have a tendency to form the Fe-O-Co ferromagnetic cluster, and so the double-exchange mechanism will not be effective. In contrast, Zn1-x(FeCu)(x)O has a tendency to form the Fe-O-Cu ferromagnetic cluster with the charge transfer between Fe and Cu, which would lead to the ferromagnetism via a type of the double-exchange mechanism. The ferromagnetic and nearly half-metallic ground state is obtained for Zn1-x(FeCu)(x)O.