We investigate experimentally and theoretically the origin of magnetism in nanocrystalline-undoped ceria films. Our results are consistent with density-functional calculations showing that both oxygen and cerium vacancies lead to ferromagnetism. Although the number of cerium vacancies is smaller than that of oxygen vacancies, the relatively high magnetic moment of the former might result in a substantial contribution to the magnetic properties. Diluted defect magnetism is suggested as a universal feature of ferromagnetism in nonmagnetic oxides without magnetic impurities.

• Received 7 October 2008

DOI:https://doi.org/10.1103/PhysRevB.80.035202