Sol-Gel Synthesis, Structure, Morphology and Magnetic Properties of Ni(0.6)Mn(0.4)Fe(2)O(4) Nanoparticles Embedded in SiO(2) Matrix

The structure, morphology and magnetic properties of (Ni(0.6)Mn(0.4)Fe(2)O(4))(α)(SiO(2))(100−α) (α = 0–100%) nanocomposites (NCs) produced by sol-gel synthesis were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM). At low calcination temperatures (300 °C), poorly crystallized Ni(0.6)Mn(0.4)Fe(2)O(4), while at high calcination temperatures, well-crystallized Ni(0.6)Mn(0.4)Fe(2)O(4) was obtained along with α-Fe(2)O(3), quartz, cristobalite or iron silicate secondary phase, depending on the Ni(0.6)Mn(0.4)Fe(2)O(4) content in the NCs. The average crystallite size increases from 2.6 to 74.5 nm with the increase of calcination temperature and ferrite content embedded in the SiO(2) matrix. The saturation magnetization (Ms) enhances from 2.5 to 80.5 emu/g, the remanent magnetization (M(R)) from 0.68 to 12.6 emu/g and the coercive field (H(C)) from 126 to 260 Oe with increasing of Ni(0.6)Mn(0.4)Fe(2)O(4) content in the NCs. The SiO(2) matrix has a diamagnetic behavior with a minor ferromagnetic fraction, Ni(0.6)Mn(0.4)Fe(2)O(4) embedded in SiO(2) matrix displays superparamagnetic behavior, while unembedded Ni(0.6)Mn(0.4)Fe(2)O(4) has a high-quality ferromagnetic behavior.