Oxygen vacancies and defects induced room temperature ferromagnetic properties of pure and Fe-doped CeO2 nanomaterials investigated using X-ray photoelectron spectroscopy

Structural, Optical, Magnetic and Electronic-state properties of co-precipitation method synthesized pure CeO2 and Ce1-xFexO2 nanomaterials have been analysed in pursuit of room temperature ferromagnetism and creation cum storage of oxygen vacancies for technological applications. Intact cubic fluorite structure after doping with presence of defects and oxygen vacancies are confirmed by XRD and Raman analysis. The grain size distribution of all the nanomaterials in 4-5 nm range is discussed with TEM images. Core level XPS spectra of Ce-3d, Fe-2p and O-1s are discussed to account for the change in valence state of cerium ion from Ce4+ to Ce3+. Oxygen vacancies generated due to substitution of Ce4+ by Fe3+ ion at Ce ion sites are responsible for observed weak ferromagnetism. The results for weak ferromagnetism in pure CeO2 and Ce1-xFexO2 samples are explained by correlating the F-center exchange mechanism with the formation of F+ center complexes Fe3+(up arrow) - VO(down arrow) - Ce3+(up arrow) and Ce3+(up arrow) - VO(down arrow) - Ce4+(up arrow) enjoined by oxygen vacancies.