Microstructure and Magnetic State of Fe₃O₄-SiO₂Colloidal Particles

Abstract

Colloidal particles consisted of individual nanosized magnetite grains on the surface of the silica cores were obtained by two-stage sol-gel technique.Size distribution and microstructure of the particles were analyzed using atomic force microscopy, X-ray diffraction and Nitrogen thermal desorption.Magnetic properties of the particles were studied by the method of the longitudinal nonlinear response.It has been shown that nanoparticles of magnetite have a size corresponding to a superparamagnetic state but exhibit hysteresis properties.The phenomenon was explained using the magnetostatic interaction model based on the hypothesis of iron oxide particles cluster aggregation on the silica surface.