纳米结构CoxFe(3-x)O4多孔微球的磁性及交换偏置效应研究

Magnetic properties and exchange bias effect of nano-structure Co_xFe_(3-x)O_4 porous microspheres

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-xO4多孔微球为立方多晶结构,其直径约300nm,是由约30nm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Ms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 CoxFe3-x O4 porous microspheres are synthesized in ethylene glycol（EG） solution,using FeCl3 · 6H2O,CoCl2·6H2O and NH4Ac 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 CoxFe3-x O4 porous 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（Ms） 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,CoxFe3-x O4 porous microspheres possess remarkable exchange bias effects at low temperatures.