The Electronic Structures and Ferromagnetism of Cu-Doped ZnO: the First-Principle Calculation Study

We have carried out first-principle spin-polarized calculations to investigate the electronic structures and the magnetic properties of Cu-doped wurtzite ZnO. It was found that the Cu-Zn substitution can introduce 1 mu (B) local magnetic moment into the doped system, whereas the ferromagnetic coupling between Cu(Zn)s is so weak that the system cannot keep ferromagnetism at higher temperature. In Zn vacancy (V-Zn) and Cu-Zn coexisted system, Cu is in the Cu (2+)/Cu (3+) mixed valence under the influence of acceptor defect V-Zn. Cu-3d electrons couple with O(around V-Zn)-sp electrons and then form Cu2+ -V-Zn -Cu2+ or Cu2+ -VZn--Cu3+ bound magnetic polaron (BMP) in the range of 1.27 similar to 1.90 nm. The overlapping between BMPs is the main ferromagnetism origin of ZnO/Cu. According to our analysis, we thought that ZnO/Cu system will display stronger ferromagnetism when the Cu concentration attains 3% in atomic percentage. The calculated results and analysis will shed light on the origin of ferromagnetism in ZnO/Cu.