Sheet magnet having microcrystalline structure and method of manufacturing the same, and method of manufacturing isotropic permanent magnet powder

摘要

An object of this invention is to provide a thin-film magnet having a residual magnetic flux density Br of not less than 10 kG, a cost performance equal to that of a hard ferrite magnet, and a thickness of 70-300 &mgr;m contributing to the miniaturization and thinning of a magnetic circuit, and a method of manufacturing the same. When a molten alloy of a predetermined structure having a small content of a rare earth element is subjected to continuous casting using a cooling roll in an inert gas atmosphere with reduced pressures of not more than 30 kPa at a predetermined peripheral speed of the roll, it turns into a crystalline structure substantially not less than 90% of which comprises a Fe₃B type compound and a compound phase having &agr; —Fe and Nd₂Fe₁₄B type crystalline structures compatible with the former. A continuous thin-film magnet of 70-300 &mgr;m in thickness comprising a microcrystalline structure of 10-50 nm in average crystal grain diameter having magnetic characteristics of iHc≧2 kOe, Br≧10 kG and practically usable as a permanent magnet can be obtained. A thin-film magnet which has heretofore been difficult to be industrially produced can be mass-produced at a low price by a simple method.