Ferromagnetic Stabilization of Eu-doped GaN Enhanced by Ga-vacancies

We report that the ferromagnetic states are stabilized by the double exchange interaction which enhanced by partially occupied N-2p hole band caused by Ga-vacancies in Eu-doped GaN, based on self-interaction-corrected (SIC) local density approximation. Eu-doped GaN is renowned for red light emitting diodes (LEDs), whereas it is interesting as a circular-polarized emission in the magnetic materials. In this study, we used a constant volume assumption and the coherent potential approximation (CPA) in the Korringa-Kohn-Rostoker (KKR) method with SIC. As a result, it indicates that electron-hole doping enhances the ferromagnetic states, because the dominant magnetic interaction is changed from Zener’s p-f exchange interaction to Zener’s double exchange interaction caused by the partially occupied N-2p band. In the enhancement, a major contribution to the magnetism is derived from the Ga-vacancies more than magnetic impurities Eu, which coupled with N anti-ferromagnetically.