To produce a magnetic powder which has small sized particles, a very high coercive force, saturation magnetization most suitable for high-density recording, and moreover is superior in preserving stability.
A nitride iron base magnetic powder is produced by applying surface cladding treatment of a predetermined element to the material particles that comprises iron base oxide or hydroxide, using a stirring apparatus, and then by applying reduction treatment and nitrogen treatment. The stirring apparatus has stirring units, which are attached to the front end of two opposite rotary axes from both the upward and downward directions, and controls the number of rotations of both rotation axes. In the nitride iron base magnetic powder produced, at least iron and nitrogen are the constituent elements, at least one element among aluminum, silicon or rare-earth element is contained; at least an Fe16N2 phase is contained, the content of nitrogen to iron is 1.0-20.0 atom%, the particle is particulate or ellipsoidal in shape having an average particle size within the scope of 5-30 nm; and the saturation magnetization reduction rate, after being preserved under an atmosphere of 60°C, 90%RH for 168 hours, is 5-15%.
SASAKI YUJI
MATSUO KAZUKI
KISHIMOTO MIKIO
