Cation vacancy-induced d0 room temperature ferromagnetism was observed in nonmagnetic potassium-doped ZnO nanowires synthesized within the pores of the anodic aluminum oxide template. The ferromagnetic signature was found to be significantly enhanced in the K-doped ZnO nanowires with respect to the pristine ZnO nanowires. The photoluminescence studies clearly indicated the presence of a large concentration of zinc vacancies in the K-doped ZnO nanowires. An interesting correlation between the saturation magnetization and green luminescence intensity with the increase of K-doping had suggested that the magnetic moment originates due to Zn vacancy defects. It was expected that the incorporation of K-related defects at the Zn site might promote the formation of zinc vacancies in the system and introduce holes to stabilize the hole-mediated room-temperature ferromagnetism. For the doped ZnO nanowires the ferromagnetic response was found to be a maximum at an optimum K-concentration of 4at%. This study demonstrated that the ferromagnetism in ZnO could be tuned by controlling the cation vacancy-defects with the proper dopant in the host semiconductors.

Vacancy-Induced Intrinsic d0 Ferromagnetism and Photoluminescence in Potassium Doped ZnO Nanowires. Ghosh, S., Khan, G.G., Das, B., Mandal, K.: Journal of Applied Physics, 2011, 109[12], 123927