| Spinel-style cobalt ferrite are being extensively and thoroughly studied as one of the most promising candidates for high-density magneto-optic recording media, due to nice physical wearability, excellent chemical stability, strong magnetocrystalline anisotropy, and a large magneto-optical effect at short wavelengths. The main problem presently researched is synthesizing cobalt-based ferrites through different composition and different preparation method, hoping to obtain moderate saturation magnetization and high coercivity simultaneously in a small size of crystalline grains, and decreasing Curie point.In this thesis, ZnyCoxFe3-y-xO4 nanoparticle series are synthesized by Sol-gel spontaneous combustion method. Heat treatment process, zinc and cobalt content and minim substitutes dependence of phase structure and magnetic properties are investigated systematically in a wide range of cation content, using X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). The main results are as follows:1. Heating treatment dependence of samples' properties are studied systematically. Proper annealing temperature is found to be a important factor in preparation. Crystal structure can be optimized and magnetic properties be improved by reducing temperature rising rate and prolonging annealing time properly at high temperature range. Bettered heating treatment route can reduce 200 ℃ for the corresponding annealing temperature of best properties.2. Stucture phase transition in different temperature range are investigated. α-Fe2O3 transitional phase appears in the annealing temperature range from 550℃ to 800℃ and single-phase ZnCo ferrites with spinel structure are obtained when temperature is beyond 800 ℃. However, spinel and α-Fe2O3 phases still coexist through high temperature annealing when zinc and cobalt contents both low. α-Fe2O3 disappears and single-phase ZnCo ferrite is obtained at x≥0.80 for Zn0.1CoxFe2.9-xO4 (0 |
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