Effect of Fe and V co-doping on ZnO by first principles study, electronic structure and magnetic properties

Abstract

In this paper, the magnetism of ZnO with wurtzite-type structure, when doped with Fe then co-doped with (Fe,V) was investigated by density functional theory. Furthermore, the difference between the ferromagnetic and the disordered local moment in term of magnetic energy indicated the stabilization of the magnetic phase in diluted magnetic semiconductors. It was revealed that the semi-metallic behaviour in Zn0.95Fe0.05O composition was transferred to a half-metallic behaviour with co-doping with V. Hence, the Fermi level was crossed by the majority-spin valence states, meanwhile, a gap occured in the Fermi level of the minority-spin states. A large replacement splitting was detected between V 3d states of the majority-spins and the minority-spins. The estimated Curie temperature was found to increase with V content. X-ay diffraction Rietveld analysis revealed that the co-doping of ZnO with Fe and V maintains the wurtzite crystal structure and that the crystallite size increased with doping concentration, i.e. 15–52 nm. Hysteresis loops indicated the appearance of room temperature ferromagnetism, where the magnetic properties were found to be very sensitive to the nature of the doping element (Fe and Fe-V) as well as its concentration. Both ab initio calculations and experimental results were found in good agreement. The observed changes in the magnetic parameters were attributed to a combination of various parameters, such as the substitution by the magnetic Fe and the non-magnetic V atoms, formation of small crystals in the nanoscale regime, the increase of crystallite size and grain boundaries.