PURPOSE: To obtain fine ferrite magnetic powder of Co-substituted of hexagonal system suitable as recording material of high-density vertical magnetization, having improved dispersibility, by preparing frozen precipitate obtained from an aqueous solution containing constituent element ion of barium ferrite of hexagonal system, thawing it with a water-soluble organic solvent.
CONSTITUTION: A solution of water-soluble salts of elements necessary for constituting the barium ferrite (preferably one having a composition shown by the formula) in water is prepared. An alkali solution such as NaOH solution, etc. having ≥9pH is added to the aqueous solution, so that a precursor is precipitated. The precipitate is usually washed with water fully, and frozen with liquid N2, etc. This frozen precipitate is added to a water-soluble organic solvent (e.g., methanol, or ethanol), and thawed. After the thawing is over, the cake of the precipitate is collected by filtration, dired, heat-treated at a given temperature, and crystallized to give the desired magnetic powder for magnetic recording.
MAEDA TATSUMI
ANAMI TAKASHI
IDO TADASHI
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