Synthesis and magnetic properties of monodisperse CoFe2O4 nanoparticles coated by SiO2 |
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Authors: | Dengwei Hu Fan Zhao Zhen Zhang Lei Miao Rong Ma Weixing Zhao Lijun Ren Gaini Zhang Le Zhai Dongmei Wang Shumei Dou |
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Affiliation: | Faculty of Chemistry and Chemical Engineering, Engineering Research Center of Advanced Ferroelectric Functional Materials, Key Laboratory of Phytochemistry of Shaanxi Province, Baoji University of Arts and Sciences, 1 Hi-Tech Avenue, Baoji, Shaanxi 721013, PR China |
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Abstract: | The monodisperse CoFe2O4 nanoparticles were synthesized by a modified chemical coprecipitation method. Coating SiO2 on the surface of the CoFe2O4 nanoparticles was carried out to keep single domain particles non-interacting with cubic magnetocrystalline anisotropy. The Curie temperatures (Tc) of the monodisperse CoFe2O4 nanoparticles can be accurately measured because the SiO2 shells prevented the aggregation and growth of nanoparticles at high temperature. The magnetic properties of the CoFe2O4@SiO2 nanoparticles with core-shell structure in a wide temperature range (300~950?K) were investigated. It is remarkable that the coercive field (Hc) of CoFe2O4 nanoparticles increased from about 760?Oe to 1806?Oe after being coated with SiO2, which increased by 137.6% compared to the uncoated samples at 300?K. The saturation magnetization (Ms) of the CoFe2O4@SiO2 nanoparticles is 34.59?emu/g, which is about 52% of the naked CoFe2O4 nanoparticles value (66.51?emu/g) at 300?K. The hysteresis loops of the CoFe2O4@SiO2 nanoparticles showed an orderly magnetic behavior at high temperature, such as the Ms, remanence magnetization (Mr) and Hc decreased as temperature increasing, being equal to zero near Tc. This is a good indication that the CoFe2O4@SiO2 nanoparticles are suitable for a wide variety of technological applications at high temperature. |
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Keywords: | Magnetic properties Core-shell Monodisperse |
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