Structure and magnetic properties of synthesized fine cerium dioxide nanoparticles

Cerium dioxide, which is diamagnetic in its bulk crystalline fluorite form, exhibits ferromagnetism when prepared as a nanopowder. This characteristic has recently been ascribed to localized electron spin moments formed at oxygen vacancies near the nanoparticle surfaces. In the present study, a number of structure-sensitive and magnetic methods were applied to CeO2 nanopowders prepared from the carbonate precursor by treatment at different calcination temperatures. The low-temperature magnetization measurements subsequently performed via 57Fe Mössbauer spectroscopy revealed the presence of small amounts of iron impurities in the samples as well as in the chemicals used to prepare them. These experimental findings and our theoretical data analysis of iron impurities at the ppm level provide a plausible explanation for the ferromagnetic behaviour of cerium oxide.