Optical and ferromagnetic properties of hydrothermally synthesized CeO2/CuO nanocomposites

Nanostructured CeO2/CuO composites are synthesized using a facile hydrothermal reaction. Results signify that Cu ions prefer to enter into CeO2 lattice forming solid solution at low concentration, and would be transformed into CuO phase at moderate concentration. Moreover, the addition of CuO species into CeO2 promotes the reduction of Ce4+ and the creation of oxygen vacancy (VO) defects. Raman analyses confirm VO concentration initially increases and then decreases with the increasing CuO phase and the sample Ce1Cu2 exhibits the highest defect concentration. The room temperature ferromagnetic behavior is observed firstly in CeO2/CuO nonmagnetic system and the maximal saturation magnetization appears in Ce1Cu2. The emergent ferromagnetism appears to be relevant to the extensive VO defects, which can be interpreted by the indirect double-exchange model. The synthetic interaction between CeO2 and CuO results in the redshift of the bandgap in prepared CeO2/CuO nanocomposites.