Synthesis of nanocrystalline spinel CoFe2O4 via a polymer-pyrolysis route

Nanocrystalline CoFe2O4 spinel ferrites were synthesized via the pyrolysis of polyacrylate salt precursors prepared by in situ polymerization of metal salts and acrylic acid. The pyrolytic behaviors of the polymeric precursors were analyzed by use of simultaneous thermogravimetric and differential thermal analysis (TG-DTA). The structural characteristics of the calcined products were obtained by powder X-ray diffraction (XRD), infrared spectroscopy (IR) and transmission electron microscope (TEM). The results revealed that cobalt ferrites had nano-sized morphology and good crystallinity even if calcined at moderate temperature like 500 °C for 3 h. The average size of nanocrystalline cobalt ferrites ranged from 20 to 30 nm with a narrow size distribution, while the particle size increased with the increase of the calcination temperature. Magnetic properties were obtained at room temperature using a vibrating sample magnetometer. The samples exhibited hysteresis loop typical of magnetic behaviors, indicating that the presence of an ordered magnetic structure could exist in the mixed spinel system. The as-calcined cobalt ferrites at 500 °C exhibited the highest magnetization value of 77.4 emu/g at 10 kOe, while the highest remanence and coercivity of 35.6 emu/g and 1445 Oe, respectively, for those calcined at 700 °C were obtained.