The University Of Tokyo

Dowa Electronics Materials Co., Ltd.

Dowa Holdings Co., Ltd.

Kazuhiro Yamaga

Kenji Sakane

Tetsuya Kawahito

Shin-ichi Ohkoshi

Toshihiko Ueyama

Asuka Namai

Hiroko Tokoro

Marie Yoshikiyo

Yasuto Miyamoto

Yuki Mineyama

A raw material solution containing trivalent iron ions, or trivalent iron ions and ions of a metal element that partially substitutes Fe sites, and an alkaline aqueous solution for neutralizing the raw material solution are added to a reaction system to adjust the pH of the reaction system from 1.0 to 3.0 or lower. Hydroxycarboxylic acid is added to the obtained reaction solution and the pH of the reaction system is then neutralized from 7.0 to 10.0 or lower. The obtained precipitate of a substituent metal element-containing iron oxyhydroxide is coated with silicon oxide, followed by heating so as to form particles of ε-iron oxide in which Fe sites are partially substituted by other metal elements, and then, a slurry containing the particles is classified. The iron-based oxide magnetic powder has a particle shape close to a perfect sphere and is suitable for use in a magnetic recording medium.

Iron-based oxide magnetic powder and method for producing same

An object of the present invention is to provide a magnetic powder having a narrow particle size distribution of epsilon-type iron oxide particles, and another object is to provide magnetic powder suitable for magnetic recording medium by improving particle size distribution, and provide epsilon-type iron oxide magnetic particles and related technologies in which a number average particle diameter of major diameters (D) is 10 to 20 nm, a 90% cumulative particle diameter (D) is 30 nm or less, and a geometric standard deviation (&#x3c3;) of major diameters is 1.45 or less, which are obtained by TEM observation.

Epsilon-type iron oxide magnetic particles and method for producing the same, magnetic powder, magnetic coating material and magnetic recording medium containing magnetic particles

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Tokyo, Japan

Kazuhiro Yamaga