On the origin of ferromagnetism in CeO2 nanocubes

Magnetic behaviors of pure CeO(2) nanoparticles and nanocubes have been investigated both experimentally and theoretically. It is found that monodisperse CeO(2) nanocubes with an average size of 5.3 nm do show ferromagnetic behavior at ambient temperature with a saturation magnetization of about 5.7 memu/g and coercive force of about 69 Oe. First-principles calculations reveal that oxygen vacancies in pure CeO(2) cause spin polarization of f electrons for Ce ions surrounding oxygen vacancies, resulting in net magnetic moment for pure CeO(2) samples. One oxygen vacancy at surface can induce more magnetic moments than those induced by one oxygen vacancy in bulk. The results obtained here provide evidence that pure CeO(2) sample with oxygen vacancies can indeed have magnetic behavior. This study will stimulate more investigations for understanding the origin of ferromagnetic TM-doped CeO(2) (TM=3d transition metals) in a particular case and TM-doped semiconductor oxides in general at ambient temperature. (C) 2008 American Institute of Physics.