Large magnetic circular dichroism of Co clusters in Co-doped ZnO

Abstract

Large magnetic circular dichroism (MCD) in Co-doped ZnO films is reported. The Co-(∼20%) doped ZnO films with oxygen deficiencies show ferromagnetic behavior at room temperature. While paramagnetic films exhibit a small MCD signal, broad MCD spectra with large amplitude of ∼20kdeg∕cm are observed for the ferromagnetic films. In the ferromagnetic films, Co cluster formation occurs, especially near the interface between the substrate and the film. The amount of the Co clusters is consistent with the spontaneous magnetization and the amplitude of the MCD.