Nanocomposites of ZnFe2O4 in silica: synthesis, magnetic and optical properties

Transparent magnetic nanocomposites with zinc ferrite nanoparticles uniformly dispersed in silica matrix have been successfully synthesized. Due to the compositional homogeneity in the starting precursor, a much lowered formation temperature of ZnFe2O4 in the nanocomposites was observed as compared to that in the conventional ceramic processing. Studies of the influence of the initial drying temperature on particle size of zinc ferrite suggest that a well-established silica network provides more confinement to the growth of ZnFe2O4 particles. The magnetic properties exhibit a strong dependence on the particle size as a result of the unusual cation distribution and the surface effect. The optical properties of the nanocomposites can be adjusted by varying the concentration of zinc ferrite nanoparticles in the amorphous silica matrix. The absorption edge at around 600 nm is blue shifted by 0.65 eV when the loading of ZnFe2O4 particles is decreased from 30 to 5 wt.%, while the absorption coefficient remains below 400 cm−1 in the red visible region.