Impact of annealing temperature and ferrite content embedded in SiO2 matrix on the structure, morphology and magnetic characteristics of (Co0.4Mn0.6Fe2O4)δ (SiO2)100-δ nanocomposites

Highlights: • Superparamagnetic CoFe₂O₄ and MnFe₂O₄ obtained by sol-gel synthesis at 1200 °C. • Crystallite size of ferrites increase with increasing annealing temperature. • Magnetic properties of ferrites increase with increasing annealing temperature. • NiFe₂O₄ and CuFe₂O₄ are paramagnetic, while ZnFe₂O₄ is ferromagnetic at 1200 °C. -- Abstract: In this work, the (Co_0.4Mn_0.6Fe₂O₄)_δ (SiO₂)_100-δ (δ = 0–100%) nanocomposites were synthesized via a modified sol-gel method followed by annealing at 200, 400, 700 and 1100 °C. The main purpose of this paper is to find a relationship between the nanoparticle structure and morphology and the magnetic parameters at different annealing temperatures and different ferrite contents embedded in the SiO₂ matrix. The powder X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were used to investigate the structural properties, such as crystalline phases, degree of crystallinity, crystallite size and the formation of chemical bonds, while transmission electron microscopy (TEM) was used to examine the morphological features of nanocomposites. The dependence of saturation and remanent magnetizations, coercivity and magnetic anisotropy on ferrite content embedded in SiO₂ matrix were investigated by vibrating sample magnetometry (VSM). The XRD data showed that the crystallite size increase with increasing annealing temperature and amount of ferrite content embedded in the SiO₂ matrix. The SiO₂ matrix exhibits diamagnetic behavior with a small ferromagnetic fraction, Co_0.4Mn_0.6Fe₂O₄ embedded in SiO₂ matrix presents superparamagnetic-like behavior, while unembedded Co_0.4Mn_0.6Fe₂O₄ a high-quality ferromagnetic type behavior.