Valence state dependent room-temperature ferromagnetism in Fe-doped ceria nanocrystals

Room-temperature ferromagnetism was observed in undoped and Fe(2+(3+))-doped CeO(2) nanocrystals. In Fe-doped samples the enhancement of ferromagnetic ordering occurs by changing the valence state of Fe ions, whereas Raman spectra demonstrated strong electron-molecular vibrational coupling and increase in oxygen vacancy concentration. Air annealing showed degradation of ferromagnetic ordering and appearance of hematite phase in Fe(3+)-doped sample. The observed ferromagnetic coupling in Fe-doped samples, associated with the presence of magnetic ions mediated by single charged O(2-) vacancies, demonstrated that valence state of dopant has a strong influence on magnetic properties of CeO(2) nanoparticles. (C) American Institute of Physics. [doi: 10.1063/1.3431581]