Nanocomposites containing Cr2O3 particles having dimensions in the range 13-35 nm dispersed in a silica matrix have been prepared by a chemical method. X-ray diffraction investigation and high resolution electron microscopy substantiate the formation of Cr2O3 particles. X-ray photoelectron spectroscopy studies show the presence of a small amount of CrO2. The samples exhibit ferromagnetic property below 300 K with the hysteresis loop showing an exchange bias. The latter is explained as arising due to exchange interaction between the spins associated with Cr 3+ and Cr4+ ions. Dc electrical resistivity measurements were analysed by a small polaron hopping model confirming the presence of Cr4+ ions at the surface of the particles. At temperatures above 100 K the magnetic hysteresis loop shift was such that zero magnetization was observed only for the negative magnetic field. This was explained as being due to a disorder effect on the magnetic spins of Cr4+ ions.
ASJC Scopus subject areas
- Condensed Matter Physics
- Electronic, Optical and Magnetic Materials
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films