NANOCRYSTALLINE Ni-Zn FERRITES PREPARED BY SOL-GEL METHOD

Nanocrystalline Ni-Zn ferrites have been synthesized in silica matrix by sol-gel processing and thermal treatment at 1100 oC. Samples with weight fraction of 20 % Ni1-xZnxFe2O4 in silica matrix were obtained for x = 0.15, 0.35, 0.50, 0.65 and characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Mössbauer spectroscopy (MS) at room temperature and vibrating sample magnetometry (VSM) measurements. The cubic spinel structure is proved both by XRD and Mössbauer spectroscopy. The ferrites embedded in the matrix have nanoparticles in the range 5-13 nm. The obtained composites, display superposed superparamagnetic and ferrimagnetic behavior, as a function of Zn/Ni ratio. Both lattice constant parameter and average hyperfine fields vary with the degree of substitution of nickel ions with zinc ones