Vacancy-induced intrinsic <i>d</i> ferromagnetism and photoluminescence in potassium doped ZnO nanowires

Abstract

Cation vacancy-induced d0 room temperature ferromagnetism was observed in nonmagnetic potassium (K) doped ZnO nanowires (NWs) synthesized within the pores of the anodic aluminum oxide template. The ferromagnetic signature was found to be significantly enhanced in the K-doped ZnO NWs with respect to the pristine ZnO NWs. The photoluminescence studies clearly indicated the presence of a large concentration of zinc vacancies in the K-doped ZnO NWs. An interesting correlation between the saturation magnetization and green luminescence intensity with the increase of K-doping has suggested that the magnetic moment originates due to Zn vacancy defects. It is 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 NWs the ferromagnetic response was found to be a maximum at an optimum K-concentration of 4 at. %. This study demonstrates that the ferromagnetism in ZnO can be tuned by controlling the cation vacancy-defects with the proper dopant in the host semiconductors.