Magnetic properties and exchange bias effect of nano-structure Cox Fe3 - x O4 porous microspheres

Nano-structure Co-x Fe3 - x O-4 porous microspheres are synthesized in ethylene glycol (EG) solution, using FeCl3 center dot 6H(2)O, CoCl2 center dot 6H(2)O 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 Co-x Fe3 - x O-4 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 (M-s) and the Curie temperature (T-c) first increase and then decrease, and the coercivity (H-c) increase with the increase of Co2+ content. According to the hysteresis loops at different temperatures, Co-x Fe3 - x O-4 porous microspheres possess remarkable exchange bias effects at low temperatures.