PURPOSE: To increase the coercive force of magnetic iron oxide by dispersing the iron oxide in an aqueous medium, removing water soluble substances contained in the iron oxide with an ion exchange resin, and depositing a Co-base metallic compound on the surface of the iron oxide.
CONSTITUTION: Magnetic iron oxide such as γ-Fe2O3 is dispersed in an aqueous medium such as water or acohol to prepare a slurry, and by adding an ion exchange resin to the slurry, water-soluble substances contained in the iron oxide are removed. As the ion exchange resin a cation exchange resin or an anion exchange resin is used, and the amount of the resin is about 0.5W100 times the theoretical amount required to exchange ions produced from the water soluble substances. A Co-base metallic compound is then deposited on the surface of the magnetic iron oxide. Metals to be deposited includes Co, Fe, Mn, Zn, Ni, Cr, Pb and Sn.
ISHIKAWA TSUNEO
MARUO SEIGOU
ASANO KIYOSHI
AMANO MASATOSHI
