Observation of room temperature ferromagnetism in Ga:ZnO:: A transition metal free transparent ferromagnetic conductor

This paper reports our results on room temperature ferromagnetism characteristics in Ga-doped ZnO. The Ga-doped ZnO films were grown epitaxially on (0001) sapphire with Ga concentration up to 5 at. %. Detailed x-ray diffraction and high resolution transmission electron microscopy results showed a high-quality epitaxy without the presence of any secondary phases. Magnetic measurements showed characteristic ferromagnetism behavior with room temperature coercivity similar to 50 Oe, which remained fairly constant with temperature. Upon annealing coercivity disappeared with typical diamagnetic characteristics of ZnO. The x-ray photoelectron spectroscopy and electrical measurements as function of annealing showed a critical role of vacancies and Ga-vacancy complexes to be critical for the observed ferromagnetic behavior. (C) 2008 American Institute of Physics.