Effect of Surface Modifications on the Magnetic Properties of Ni 0.5Zn 0.5Fe 2O 4 Nanoparticles

Abstract

Two different silica sources have been used for the preparation of Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites, and their effects on the particle size, crystallinity and the magnetic properties have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and physical property measurement system (PPMS). In both cases, Ni0.5Zn0.5Fe2O4 nanoparticles of 11 nm in mean particle size were well dispersed in silica matrix. The coercivity and the blocking temperature of Ni0.5Zn0.5Fe2O4 nanoparticles modified with the silicon coupling agent show little decrease, whereas the saturation magnetization increases obviously with respect to nanoparticles dispersed directly in silica matrix. It is considered that the decrease of the surface anisotropy resulting from the change in the surface coordination is responsible for the observed behavior.