急冷凝固したストロンチウムフェライトの組織と磁性

抄録

Amorphous formation regions for the pseudo-ternary SrO-Fe₂O₃-B₂O₃ system were investigated using melt spinning and water quenching techniques. The specimens were heat treated, and then examined to determine the composition and temperature ranges where the M-type ferrites precipitated, and the relationship between crystalline phases and magnetic properties was discussed.
The amorphous formation region by melt spinning is restricted within the composition range of less than 60 mol%Fe₂O₃ and 60-70 mol%SrO, and that by water quenching within the composition range of less than 25 mol%Fe₂O₃ and more than 30 mol%B₂O₃.
The region, where M-type ferrites are crystallized by heating, is divided into two: one is the area where the particle size and coercive force of M-type ferrite depend on cooling rate, and the other is the area where they are independent of cooling rate. In the former, the composition ranges are determined where fine M-type ferrite particles of high coercive force (higher than 320 kA/m (4 kOe)) precipitate from the heat-treated amorphous phases. Although the maximum coercive force of 560 kA/m (7000 Oe) is obtained in the latter, fine particles smaller than a superparamagnetic particle size are also formed.