Tunable Ferromagnetic Behaviors Observed in Highly Orientated Co-Doped ZnO Thin Films by the Bandgap Engineering.

Highly orientated Co-doped Zn( Mg, Cd) O thin films have been prepared on Si (001) substrate using pulsed laser deposition (PLD). Our results indicate that Mg and Cd-doping can tune the bandgap of ZnO thin film. Apparent room-temperature ferromagnetism is observed in these films, which can be modified by the bandgap of ZnO. A narrow bandgap enhances the ferromagnetism of the films through the Cd-doping, and wide bandgap does the opposite through the Mg-doping, which may be ascribed to the ferromagnetic ( FM) exchange interaction between the 3 d states of magnetic Co ions and the impurity band. These experimental results provide some new evidence that the ferromagnetism in Co: ZnO is closely related to crystal defects and improve our knowledge about ferromagnetism in dilute magnetic oxides. [ABSTRACT FROM AUTHOR]