The oxygen vacancies correlated ferromagnetism in transition metal-doped ZnO nanowires

Dilute magnetic semiconductors (DMSs) have attracted much attention over the last decades due to their possibility of manipulating charge and spin degrees of freedom in a single substance. Extensive experimental investigations on ferromagnetism (FM) in transition metal (TM) doped ZnO have been concentrated on thin film and nanograin systems. However, up to now the debate on the origin of FM in TM doped ZnO still exists. Recently, there are some experimental report on the FM of transition metal doped ZnO with the one-dimensional nanowires, nanotubes and nanobelts. For examples, the ferromagnetism with low Curie temperature T_c<;50K has been observed in Mn-doped ZnO nanowires synthesized by vapor-phase or chemical vapor deposition methods. Room temperature FM has been oberved in Mn or Co-doped ZnO nanowires prepared by solution phase method. In this work, in order to understand the role of oxygen vacancies in TM doped ZnO nanowires, ab initio calculations on the magnetism of V, Cr and Mn-doped ZnO NWs with oxygen vacancies are performed, in comparison with case without oxygen vacancies.