Effect of Electron Configuration on Defect Induced Ferromagnetism in Doped CeO₂ Nanoparticles
William Lee1*, Shih-Yun Chen1, Cheng-Wei Ku1
1Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan
* presenting author:William Lee, email:leecom93299@yahoo.com.tw
In this study, we report on the successful synthesis of Pr-doped CeO₂ (CeO₂:Pr) nanoparticles (NPs) using a co-precipitation method while setting the Pr-content in the range from 0 to 15 atom %. The as-prepared samples were characterized in regard to their structural, morphological and magnetism. At first, crystal structure was characterized by X-ray Diffraction. X-ray Absorption Spectroscopy (XAS) and Raman spectroscopy were utilized to investigate the electronic structure of these NPs. Then ferromagnetism was studied by Vibrating Sample Magnetometer (VSM) at room temperature.
It is demonstrated that as raising the content of Pr, the degree of oxygen deficiency was enhanced monotonically, suggesting that oxygen and/or oxygen-related vacancies was induced. XAS analysis indicated the preference of the Pr-ions for the Pr3+ oxidation state. But the valence state of Ce ions changed as increasing Pr content, it stayed constant at 9% then raise to 10% when Pr reaches 9%. Together all spectroscopic results, the structure and evolution of above oxygen related defect was then unraveled. Furthermore, all the Pr-doped CeO₂ NPs were found to be ferromagnetic at room temperature. The concentration dependence of dopant as well as defect on magnetism was shown and compared to other doped CeO₂ NPs with different electron configuration of dopants. At last, the relationship between defect structure and magnetic behavior of Pr-doped CeO₂ NPs was derived.

Keywords: CeO2, nano-particles, Raman, defects, ferromagnetism