Magnetic nanocomposites:: preparation and characterization of Co-ferrite nanoparticles in a silica matrix

Magnetic nanocomposites of Co-ferrite nanoparticles dispersed in silica matrix (CoFe2O4/SiO2) have been prepared by the sol-gel technique using tetraethylorthosilicate (TEOS) as precursor of silica, and metallic nitrates as precursors of ferrite. Samples prepared in powder form have been dried at 100 C for 3 h and calcined for 2 h at temperatures between 500 and 1000 C. Co-ferrite particles were formed in the matrix pores and the nucleation of these particles was observed with the increase in the calcining temperature. TEM measurements showed that the nanoparticles had a fairly uniform morphology and an average particle size of approximately 5 nm. The combination of different Co-ferrite concentrations and calcining temperatures allowed to obtain samples with saturation magnetization ranging from 0.7 to 21.8 emu/g. (C) 2003 Elsevier B.V. All rights reserved.