Composition and magnetic properties of cobalt ferrite nano-particles prepared by the co-precipitation method
Composition and magnetic properties of cobalt ferrite nano-particles prepared by the co-precipitation method
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DOI：
10.1016/j.jmmm.2010.06.047
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发表时间：
2010-11
影响因子：
2.7
通讯作者：
Yue Zhang;Zhi Yang;D. Yin;Y. Liu;Chunlong Fei;R. Xiong;Jing Shi;G. Yan
中科院分区：
文献类型：
--
作者：
Yue Zhang;Zhi Yang;D. Yin;Y. Liu;Chunlong Fei;R. Xiong;Jing Shi;G. Yan
采用共沉淀法制备了钴铁氧体纳米粒子，并对其进行了退火处理。通过X射线衍射、拉曼光谱、热重-差热分析和透射电子显微镜等测试手段，证实了所制备的纳米粒子具有不同的组成、结构和尺寸。在室温下测量的磁滞回线显示，通过向Co2+和Fe 3+离子的混合溶液中加入NaOH溶液制备的样品，由于Co 3+离子的形成，其有效磁各向异性常数、矫顽力和剩磁比较小。在NaOH溶液中加入Co2+和Fe 3+离子的混合溶液制备的纳米颗粒具有较小的饱和磁化强度和较强的矫顽力，这与钴铁氧体纳米颗粒表面形成了结晶较差的外层有关。在200和300°C下，这些外层的存在诱导了钴铁氧体纳米晶体中Co2+离子的氧化，导致了组成和磁性能的大幅度变化。
Cobalt ferrite nano-particles were prepared using the co-precipitation method followed by annealing treatment. The formation of nano-particles with different composition, microstructure and sizes were confirmed by X-ray diffraction, Raman, thermogravimetric-differential thermal analysis and transmission electron microscope. The magnetic hysteresis loops measured at room temperature revealed smaller effective magnetic anisotropy constant, coercivity and remanence ratio for the samples prepared by adding the NaOH solutions into the mixed solutions of Co2+and Fe3+ions due to the formation of Co3+ions. A small saturation magnetization and an enhanced coercivity were observed for the nano-particles prepared by adding the mixed solutions of Co2+and Fe3+ions into the NaOH solutions, which was related to the formation of outer layers with poor crystallization on the surfaces of the cobalt ferrite nano-crystals. Furthermore, the existence of these outer layers induced the oxidation of Co2+ions in cobalt ferrite nano-crystals at 200 and 300°C, and led to a large change on the composition and magnetic properties.