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

• Published in: Physica. B, Condensed matter Condensed matter, 2012-08, Vol.407 (16), p.3218-3221
• Main Authors: Ferreira, N.S., Abraçado, L.G., Macêdo, M.A.
• Format: Article
• Language: English
• Subjects: CeO2; Chromium; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Exchange and superexchange interactions; Ferromagnetism; Magnetic properties and materials; Magnetic properties of nanostructures; Magnetically ordered materials: other intrinsic properties; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Materials science; Nanoparticles; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Physics
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2011.12.069

We report an investigation of the nature of room-temperature ferromagnetism enhancement in Ce1−xCrxO2−δ 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 Ce1−xCrxO2−δ samples at 27 oC showed a maximum remanent magnetization value of 0.01emu/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.