Fabrication And Investigation Of Room Temperature Ferromagnetism In CeO₂ Based Nanoparticles

Information technology is important in the development of human society, where the scale and speed of information processing, transmission and storage is the key issue for its development. Magnetic semiconductor materials utilize both the charge and spin properties of electron are considered to be the next generation of electron spin devices. Therefore, the investigation of magnetic semiconductor materials is significant and essential not only from the point of view of fundamental physics but also for their practical applications. This thesis mainly discusses the origin of room-temperature ferromagnetism and how to regulate its magnetic properties based on CeO₂ nanoparticles, as well as, Cu and Al doped CeO₂ nanoparticles.Pure CeO₂ nanoparticles were fabricated by a co-precipitation method, the samples’ structure and magnetic properties were investigated. Both samples show ferromagnetic at room temperature. It is found that the ferromagnetic properties of both samples can be tuned by changing the post-annealing and hydro-thermal conditions. The oxygen vacancies at the surface were deduced to be the reason causing the ferromagnetic behaviors of CeO₂ nanoparticles at room temperature.Cu doped CeO₂ nanoparticles were also prepared by the co-precipitation method with post-annealing. Second phase was not detected by XRD and XPS. The magnetic measurement results indicate that the Ms of the samples increases as the increasing of Cu concentration, which can be explain by the BMP model.Low concentration of Al doped CeO₂ nanoparticles were also prepared by the co-precipitation method with post-annealing. Results indicate that all the samples show clear room temperature ferromagnetism. And the Ms for the Al doped CeO₂ nanoparticles is larger than that of pure CeO₂, which may be caused by the introduction of Al.