ZnO-based nanostructures for diluted magnetic semiconductor

Since the prediction by Dietl et al. in the year 2000, extensive research activities have been focused on the ZnO-based diluted magnetic materials (DMSs). Earlier works were mainly performed using bulk or thin film materials with transition-metal doping, and diverse magnetic properties including ferromagnetism, paramagnetism, and diamagnetism have been reported. Identifying the dominant mechanism of the ferromagnetic ordering and realizing reproducible ferromagnetism above room temperature have been the main research issues, but a consensus is still lacking even today. Recently, reports on ZnO nanostructures with ferromagnetic behavior have been growing due to the novel properties brought about by the high surface-to-volume ratio and surfaces rich in defect states. In this review, we focus primarily on the recent progress in experimental studies of nanostructure ZnO DMSs. We shall separate our discussion into 2 categories as Mn- and Co-doped ZnO and undoped ZnO nanostructures reported in the literature.