Magnetic and structural properties of CeO$_{2}$ nanoparticles

Nanoparticles of cerium oxide, CeO$_{2}$, have potential applications in catalysis, fuel cells, microelectronics etc [1]. In this work, we have investigated the magnetic and structural properties of 10{\%}CeO$_{2}$ supported on SiO$_{2}$ aerogel with a BET surface area $\approx $ 700 m$^{2}$/g. X-ray diffraction (XRD) studies show cubic CeO$_{2}$ as the dominant phase with particle size $\approx $ 3 nm. Temperature variation (2K -- 350K) of the magnetic susceptibility $\chi $ shows Curie-type variation with the Curie constant C = 5.9 $\times $ 10$^{-5}$ emu K/g Oe. In electron magnetic resonance (EMR) studies from 5 K to 300 K at 9.28 GHz, an EMR line at g $\approx $ 2.1 with linewidth $\Delta $H $\approx $ 100 Oe is observed for T $<$ 40 K. Since Ce$^{4+}$ in CeO$_{2}$ is diamagnetic, we tentatively suggest that the observed Curie variation of $\chi $ and the EMR line [2] are due to paramagnetic Ce$^{3+}$ present in oxygen-lean CeO$_ {2}$ nanoparticles. From the magnitude of C, the concentration of Ce$^{3+}$ is estimated to be $\approx $ 3 {\%}. Further studies are in progress. [1]. S. Sathyamurthy et al, Nanotechnol. \underline {16}, 1960 (2005). [2]. D. Schaniel et al, Phys. Rev. B \underline {70,} 144410 (2004).