Oxygen Vacancy Dependent Magnetism of CeO2 Nanoparticles Prepared by Thermal Decomposition Method

This study reports that highly oxygen-deficient CeO2 nanoparticles (NPs) can be obtained without reduction treatment by using thermal decomposition method. Different amounts of surfactants are used to control the size of the NPs. The X-ray absorption near-edge spectra (XANES) indicate that the concentration of Ce3+ is higher than 20% for all NPs. It is also found that most Ce3+ locates at the surface. Magnetic-measurement results show that room-temperature ferromagnetism (FM) of the CeO2 is closely related to the concentration of Ce3+ at the surface (IsCe3+). Saturation magnetization (Ms) reaches the maximum value with an IsCe3+ of about 40%; however, Ms decreases when IsCe3+ is raised further. The highest Ms in this study is obtained from the sample without surfactant (Ms = 0.12 emu/g). This is comparable with the results in other reports in which the CeO2 NPs were subjected to the reduction treatment. Notably, NPs become paramagnetic when IsCe3+ reaches 48%. This study suggests that oxygen vacancy is es...