Enhanced Room-Temperature Ferromagnetism in Composite CeO<inf>2</inf>/CeF<inf>3</inf> Nanoparticles

Abstract

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A considerable enhancement of the room-temperature ferromagnetism is observed in the composite CeO2/CeF3 nanoparticles. The saturation magnetization for the composite CeO2/CeF3 nanoparticles (the average particle size ≈100 nm) is more than a half order of magnitude higher compared to the initial CeO2 nanoparticles (the average particle size ≈30 nm). The composite CeO2/CeF3 nanoparticles are synthesized by fluorination of initial CeO2 nanoparticles. For this purpose, the initial ceria powder is annealed in the vacuum followed by an intake in the furnace of gaseous tetrafluoromethane (CF4). X-ray diffraction (XRD) patterns show that resulting powder has both CeO2 and CeF3 structures with the ratio CeO2/CeF3 depending on the temperature and the duration of the annealing. It is supposed that the CeF3 structure forms on the surface of the CeO2 nanoparticles as a result of the chemical reactions on the surface of the CeO2. A considerable increase of the saturation magnetization in the CeO2/CeF3 nanoparticles compared to the initial, vacuum, and air annealed CeO2 nanoparticles is supposed due to the interface CeO2/CeF3 structure produced by the applied method of fluorination. The present study suggests that adjusting the interface in the composite nanoparticles containing ceria is a perspective way to enhance the room temperature ferromagnetism.