Structure and magnetic properties of CoFe2O4/SiO2 nanocomposites obtained by sol-gel and post annealing pathways

The influence of the CoFe2O4 nanoparticles concentration in silica matrix on the structural and magnetic properties of xCoFe2O4/(100−x)SiO2 nanocomposites with x=10, 30, 50, 70 and 90 was studied. Magnetic CoFe2O4 nanoparticles dispersed in silica matrix was obtained by sol-gel method, followed by annealing at 1100 °C. The X-ray diffraction pattern and FT-IR spectra revealed the single spinel ferrite structure for all samples. The FT-IR spectra also suggested the formation of the amorphous silica matrix. The results showed that the increase of cobalt ferrite concentration (x) in the silica matrix leads to high crystallinity, specific surface area and particle size. The magnetic CoFe2O4 nanoparticles have spherical shapes and size in the 6-35 nm range. The Mössbauer measurements were fitted with two Zeeman sextets, indicating that all the samples were completely magnetically ordered. The vibrating sample magnetometer studies showed that the saturation magnetization (Ms) and coercivity (Hc) of the CoFe2O4 nanocrystals embedded in silica matrix possessed a linear relationship with the mean crystallite size. Also, the saturation magnetization of the studied nanocomposites increases with the increase of cobalt ferrite concentration (x) in the silica matrix.