FERROMAGNETIC GRANULAR POWDER AND METHOD FOR MANUFACTURING SAME, AS WELL AS ANISOTROPIC MAGNET, BONDED MAGNET, AND PRESSED-POWDER MAGNET

摘要

The present invention relates to ferromagnetic particles capable of exhibiting a high purity and excellent magnetic properties from the industrial viewpoints and a process for producing the ferromagnetic particles, and also provides an anisotropic magnet, a bonded magnet and a compacted magnet which are obtained by using the ferromagnetic particles. The ferromagnetic particles comprising an Fe 16 N 2 compound phase in an amount of not less than 80% as measured by Mössbauer spectrum and each having an outer shell in which FeO is present in the form of a film having a thickness of not more than 5 nm according to the present invention can be produced by subjecting iron oxide or iron oxyhydroxide having an average major axis diameter of 40 to 5000 nm and an aspect ratio (major axis diameter/minor axis diameter) of 1 to 200 as a starting material to dispersing treatment to prepare aggregated particles; subjecting the iron compound particles passed through a mesh to hydrogen reducing treatment at a temperature of 160 to 420°C; and then subjecting the resulting particles to nitridation treatment at a temperature of 130 to 170°C.