Ce_1−xPr_xO_2−δ (0 ≤ x ≤ 0.4) nanocrystals were synthesized by self-propagating method and thoroughly characterized using X-ray diffraction, Raman and X-ray photoelectron spectroscopy and magnetic measurements. Undoped CeO₂ nanocrystals exhibited intrinsic ferromagnetism at room temperature. Despite the increased concentration of oxygen vacancies in doped samples, our results showed that ferromagnetic ordering rapidly degrades with Pr doping. The suppression of ferromagnetism can be explained in terms of the different dopant valence state, the different nature of the vacancies formed in Pr-doped samples and their ability/disability to establish the ferromagnetic ordering.

Room-temperature ferromagnetism was observed in undoped and ${\text{Fe}}^{2+\left(3+\right)}$ -doped ${\text{CeO}}_2$ 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 ${\text{Fe}}^{3+}$ -doped sample. The observed ferromagnetic coupling in Fe-doped samples, associated with the presence of magnetic ions mediated by single charged ${\text{O}}^{2-}$ vacancies, demonstrated that valence state of dopant has a strong influence on magnetic properties of ${\text{CeO}}_2$ nanoparticles.