A novel synthesis of core/shell Co0.5Ni0.5Fe2O4/SiO2 nanomaterial and the effect of SiO2 on its magnetic properties

Abstract

Co_0.5Ni_0.5Fe₂O₄ nanoparticles have been synthesized by a stearic acid method. Core/shell Co_0.5Ni_0.5Fe₂O₄/SiO₂ nanomaterials at varying amount of SiO₂ are prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) precursor. The composition phase and average crystallite size have been characterized by means of X-ray diffraction. The particle structure and morphology of the core–shell nanoparticles are determined using transmission electron microscopy (TEM). The presence of Si-O-Si bonds for both coated samples is confirmed through Fourier transform infrared spectroscopic. Results show a decreasing saturation magnetization (M_s) when amount of TEOS is increased. The addition of SiO₂ at first instance enhance the coercivity (H_c), and maximum H_c is observed when 0.4 mL TEOS is added. However, adding more SiO₂ decrease the coercivity because the domain wall motion on the surface of nanoparticles is limited.