纳米结构CoxFe3-xO4多孔微球的磁性及交换偏置效应研究

摘要

用乙二醇为溶剂,用三氯化铁、二氯化钴和醋酸铵为起始反应试剂,通过溶剂热反应首次合成了纳米结构CoxFe3-xO4多孔微球.用X射线衍射仪(XRD)、透射电子显微镜(TEM)和扫描电子显微镜(SEM)表征样品的结构和形貌,结果表明,所制备的单分散CoxFe3-O4多孔微球为立方多晶结构,其直径约300 nm,是由约30 nm颗粒组装而成.用振动样品磁强计(VSM)测量了CoxFe3-xO4多孔微球的室温和变温磁性,室温下其饱和磁化强度M,随Co2+含量x的增加先升后降,矫顽力Hc随Co2+含量x的增大而上升;居里温度Tc随Co2+含量x的变化趋势为先增后降;低温下CoxFe3-xO4多孔微球存在显著的正交换偏置效应,这种奇特的现象还未见报道,这与其由纳米颗粒组装的多孔微球结构有密切关系.%Nano-structure Cox Fe3-xO4porous microspheres are synthesized in ethylene glycol (EG) solution, using FeCl3 ·6H2 O, CoCl2 · 6H2 O and NH4 Ac as the starting materials through solvothermal route. X-ray diffraction (XRD), scanning electron microscopy ( SEM ), and transmission electron microscopy ( TEM ) are used to characterize the structures of synthesized products. The results show that monodisperse Cox Fe3 -xO4porous microspheres with polycrystal structures are assembled by nanoparticles, and the average diameters is about 300 nm. The magnetic properties are evaluated with a vibrating sample magnetometer (VSM). The results indicate that the saturation magnetization (M4) and the Curie temperature (Tc) first increase and then decrease, and the coercivity (Hc) increase with the increase of Co2+ content.According to the hysteresis loops at different temperatures, Cox Fe3-xO4porous microspheres possess remarkable exchange bias effects at low temperatures.