The preparation of Co1-xCdxFe2O4/SiO2 nanocomposites with core/ shell structure involved the coating of SiO2 using Stöber method on Co1-xCdxFe2O4 and the use of facile thermal treatment method for synthesizing nanoparticles. The effect of cadmium substitution and SiO2 coating on the degree of crystallinity, samples composition, microstructure, and phase composition were conducted by X-ray diffraction (XRD), energy dispersion X-ray analysis (EDXA), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FT-IR), respectively. Magnetic properties were demonstrated by a vibrating sample magnetometer (VSM) which displayed that Co-Cd ferrite nanoparticles and coated silica samples exhibited magnetic behaviors. In investigating the influence of cadmium substitution and the SiO2 coating on the band gap energy (Eg), a more accurate method was used in evaluating the band gap energy (Eg). The method of evaluation is a recently proposed one known as derivation of absorption spectrum fitting (DASF) which involves the direct absorption spectra of UV-Visible region, without any need for the concentration of powders or solutions.
