Low-Temperature Preparation of Superparamagnetic CoFe2O4 Microspheres with High Saturation Magnetization

Based on a low-temperature route, monodispersed CoFe 2 O 4 microspheres (MSs) were fabricated through aggregation of primary nanoparticles. The microstructural and magnetic characteristics of the as-prepared MSs were characterized by X-ray diffraction/photoelectron spectroscopy, scanning/transmitting electron microscopy, and vibrating sample magnetometer. The results indicate that the diameters of CoFe 2 O 4 MSs with narrow size distribution can be tuned from over 200 to ~330 nm. Magnetic measurements reveal these MSs exhibit superparamagnetic behavior at room temperature with high saturation magnetization. Furthermore, the mechanism of formation of the monodispersed CoFe 2 O 4 MSs was discussed on the basis of time-dependent experiments, in which hydrophilic PVP plays a crucial role.