To provide metal magnetic grain powder for magnetic recording having a high coercive force in spite of fine particles, more particularly, fine particles of 5 to 60 nm.
The metal magnetic grain powder for magnetic recording is obtained by subjecting geothite particle powder having aluminum content of 3 to 50 atomic% expressed in terms of Al based on total Fe to heating treatment to form hematite grain powder, and then subjecting the hematite grain powder to heating reduction to obtain the metal magnetic grain powder, thence forming a surface oxide film, and subjecting the metal magnetic grain powder to heating treatment in a temperature range of 400 to 500°C under an inert gaseous atmosphere, then again subjecting the metal magnetic grain powder to heating reduction treatment and forming a surface oxide film.
COPYRIGHT: (C)2010,JPO&INPIT
Shunji Harada
Takahiro Matsuo
Yosuke Yamamoto
Kazuyuki Hayashi
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