The effects of Cr-doping on the room temperature ferromagnetism of chemically synthesized CeO2-δ nanoparticles

We report an investigation of the nature of room-temperature ferromagnetism enhancement in Ce-1_xCrxO2_(delta) nanoparticles (0.00 <= x <= 0.05), synthesized by a sol-gel-based method. Energy-dispersed X-ray spectrometry (EDS) analysis was used to estimate the dopant concentrations. The average crystallite sizes and particle size were estimated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. Both studies showed a gradual decrease in the size of the crystallites and particles for x> 0.01. Cr can substitute for Ce in the crystal lattice, and the Raman measurements indicated that structural defects in the samples increased as a function of the Cr content in the CeO2 crystal lattice. The surface topography, examined by scanning electron microscopy (SEM), showed that the undoped sample has a porous and loosely organized structure, whereas the Cr-doped samples exhibited a dense and compact structure. Magnetic measurements of the Ce-1_xCrxO2_(delta) samples at 27 degrees C showed a maximum remanent magnetization value of 0.01 emu/g for x=0.05. The nature and enhancement of room-temperature ferromagnetism was interpreted by taking into account the exchange interaction between Cr3+ ions and oxygen vacancies in CeO2. (C) 2011 Elsevier B.V. All rights reserved.