Synthesis of SiO 2 coated NiFe 2 O 4 nanoparticles and the effect of SiO 2 shell thickness on the magnetic properties

In this work, the results of synthesis of core-shell NiFe 2 O 4 nanoparticles and influence of silica coating on the magnetic properties of nanoparticles are presented. Spherical NiFe 2 O 4 nanoparticles were prepared via a normal micelles process. NiFe 2 O 4 nanoparticles homogeneously coated with SiO 2 of various shell thickness were synthesized by reverse microemulsion. The interparticle spacing was varied by changing the amount of added tetraethylorthosilicate. The microstructures and morphologies of these nanoparticles were studied by x-ray diffraction and transmission electron microscopy techniques. The magnetic parameters such as saturation magnetizations, blocking temperatures, and magnetic anisotropies have been calculated from dc magnetization and ac susceptibility measurements.