Sol–gel synthesis and characterization of single-phase CoLaxFe2−xO4 ferrite nanoparticles dispersed in a SiO2 matrix

Abstract

Single-phase CoLa_xFe_2−xO₄ (x = 0, 0.05, 0.10, 0.15, 0.20) nanoparticles dispersed in a SiO₂ (30 wt%) matrix were synthesized by a sol–gel method. The structure, magnetic properties and cation distribution of the nanocomposites were studied at room temperature. The X-ray diffraction results revealed that the lattice constant of CoLa_xFe_2−xO₄ increased initially and then decreased with increasing La³⁺ concentration x, and the ferrite average grain size was in the range of 26–39 nm, which was close to the particle size observed from transmission electron microscopy images. Field emission scanning electron microscopy analysis indicated the ferrite nanoparticles were almost spherically shaped and homogeneous. Mössbauer spectroscopy measurements suggested all the samples were completely magnetically ordered, and the distribution of cations between tetrahedral and octahedral sites changed with increasing x. The saturation magnetization and coercivity of the nanocomposites determined from vibrating sample magnetometry showed the maximum values of 43.66 emu g⁻¹ at x = 0.05 and 1685.0 Oe at x = 0.10, respectively. The improved magnetic properties will make the nanocomposites useful for applications in high density magnetic recording media.