A Comparative First-Principles Study of Fe-, Co- and FeCo-Doped ZnO with Wurtzite and Zinc Blende Structures

First-principles study of the electronic and magnetic properties of zinc-blende and wurtzite structures of Fe-, Co-, and FeCo-doped ZnO is presented. It is found that after doping, this diamagnetic material becomes ferromagnetic and half-metallic. It is also shown that the half-metallicity may be obtained for ZnFeO, ZnCoO, and ZnFeCoO. The analysis of the spin density reveals that the ferromagnetic phase is due to the ferromagnetic coupling between the p?Cd states. The effects of Fe on the magnetic properties of ZB and WZ Fe-doped ZnO compound have been investigated with the GGA calculations. In order to understand the role of Fe atom in the ferromagnetism, the density of states both in the presence and absence of Co doping, were calculated. The obtained results show the presence of coupling between Co and Fe atoms through the spin-split impurity band exchange mechanism. More importantly, the calculations show that the magnetic moment changes sensitively with the type of structure of ZnO, zinc-blende, or wurtzite. A discussion by comparing the results obtained in this study and the experimental results reported in the literature of similar systems show a very good agreement.