Manipulating Magnetism in Ce-doped SnO₂ Nanocrystals by UV Irradiation and Co Co-doping

Ultraviolet-light irradiation and Co co-doping have been used to induce magnetic property variations in Ce-doped SnO₂ nanocrystals. As demonstrated by Ce L₃-edge x-ray absorption near edge structure (XANES) data, UV irradiation generates O vacancies near Ce dopant atoms, reducing the valency of Ce ions, while leaving Co ions intact in the samples. The Ce-L₃ and Co-K extended x-ray absorption fine structure (EXAFS) analysis also show that both Ce and Co dopant atoms occupy Sn sites in the SnO₂ host. The superconducting quantum interference device (SQUID) measurements reveals room temperature ferromagnetism in (Ce,Co)-codoped SnO₂, while the diamagnetic SnO₂ host becomes paramagnetic when doped with only one of the two dopant elements. Ultraviolet-light irradiation were found to substantially enhance the ferromagnetism in the (Ce,Co)-codoped samples. Theoretical calculations based on density functional theory (DFT) were carried out to explain the experimentally observed magnetic property variations.