Tuning morpho-structural and magnetic characteristics of (Co0.5Zn0.5Bi0.2Fe1.8O4)x(SiO2)100-x nanocomposites via composition and calcination temperature

Abstract

The influence of various proportions of Co_0.5Zn_0.5Bi_0.2Fe_1.8O₄ (x = 25–100 %) dispersed in a SiO₂ matrix, as well as the effect of calcination temperature on the morpho-structural and magnetic characteristics of (Co_0.5Zn_0.5Bi_0.2Fe_1.8O₄)_x(SiO₂)_100-x nanocomposites (NCs) was explored using X-ray diffraction (XRD), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM). At all calcination temperatures, the NC with x = 100 % showed the well crystallized ferrite phase, while the NCs with x = 25–75 % displayed well crystallized ferrite phase accompagnied by cristobalite and quartz. The particle size increased progressively from about 30 nm at low calcination temperatures (300, 600 and 900 °C) to about 100 nm at 1200 °C, along with the ferrite content in the composition. The correlation between ferrite crystallite and nanoparticle size revealed that the SiO₂ outer glaze is rather a constant layer of about 2–4 nm. The remanent magnetization, saturation magnetization, coercivity and anisotropy constant increased with the ferrite content dispersed in the SiO₂ matrix. In this regard, dispersing mixed Co-Zn-Bi ferrite nanoparticles into the SiO₂ matrix minimized the particle agglomeration, and allowed a fine tuning of particle size and magnetic characteristics. The magnetic behavior tailored by particle size, ferrite content and calcination temperature enables mixed ferrites to meet the requirements of specific applications in multifunctional materials such as magnetic coatings or thin films.