Preparation and magnetic properties of Ni_(0.5)Co_(0.1)Zn_(0.4)Fe_2O_4 nanocrystalline powders by sol-gel process

摘要

The preparation process of S-type nanocrystalline ferrite Ni_90.5)Co_(0.1)Zn_(0.4)Fe_2O_4 powders by the citrate gel process has been investigated. X-ray diffraction (XRD) has been carried out to study the structural details of the ferrite. The XRD patterns were analyzed by Rietveld method (whole profile matching). The results show that the relative peak intensities of nanocrystalline ferrite have some difference with that of the ferrite prepared by coprecipitation method. Defects such as vacancies and interstitial atoms were introduced in structure model to explain the difference. Crystallite size was calculated from the full width at half maximum (FWHM) of peaks. It was found that changing the calcining temperature could control the crystallite size, which is not sensitive to heating time. Magnetic properties were measured using a vibrating sample magnetometer (VSM) with an applied field up to 8KOe. The saturation magnetization increases rapidly as the heating temperature increases. The lower saturation magnetization of nanocrystalline ferrite was also analyzed.