Synthesis of high-coercivity cobalt ferrite particles using water-in-oil microemulsions

Magnetic nanoparticles of cobalt ferrite (CoFe2O4) have been synthesized using water-in-oil microemulsions consisting of water, cetyl trimethyl ammonium bromide (surfactant), n-butanol (cosurfactant), and n-octane (oil). Precursor hydroxides were precipitated in the aqueous cores of water-in-oil microemulsions and these were then separated and calcined to give the magnetic oxide. X-ray diffraction confirmed the formation of phase pure cobalt ferrite. These nanoparticles were less than 50 nm in size and had a high intrinsic coercivity (1440 Oe) and saturation magnetization (65 emu/g).