Tunable coercivity of CoFe2O4 nanoparticles via thermal annealing treatment

High coercivity magnetic nanoparticles (CoFe2O4) have been synthesized by hydrolysis reaction in a micelle system followed by proper thermal annealing treatment to induce the crystallization. The TEM observations showed that majority of the particles are spherical in shape, fairy monodispersed and the size varied in the range of 10.0-70.0 nm. It was found that higher annealing temperatures favored the ferrite formation with larger size due to the interdiffusion process. The XRD patterns revealed that all the products consisted of nanocrystalline ferrite phase only. The magnetic properties of the products were found greatly affected by the average crystalline size of the nanoparticles. By controlling the thermal annealing treatment, the coercivity (H,) and saturation magnetization (g,) of the nanoparticles can be well tuned as a function of temperature. The current synthetic approach offered a novel development for the production of soft magnetic materials. (c) 2007 Elsevier B.V. All rights reserved.