First principles study of the magnetism driven by cation defects in CeO₂: the important role of O2p states

The magnetism driven by cation defects in undoped CeO₂ bulk and thin films is studied by the density functional theory corrected for on-site Coulomb interactions (DFT+U) with U=5 eV for the Ce4f states and U=7 eV for the O2p states. It is found that the Ce vacancies can induce a magnetic moment of the ～4μ_B/supercell, which arises mainly from the 2p hole state of the nearest neighbouring O atom (～1μ_B on per oxygen) to the Ce vacancy. The effect of the methodology is investigated, indicating that U=7 eV for the O2p state is necessary to obtain the localized O2p hole state in defective ceria with cation vacancies.