Method for producing ferromagnetic particle powder, anisotropic magnet, bonded magnet, and dust 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 layer having a thickness of not more than 5 nm according to the present invention can be produced by subjecting aggregated particles of an iron compound as a starting material whose primary particles have a ratio of [(average deviation of major axis lengths of particles)/(average major axis length of particles)] of not more than 50%, U c of not more than 1.55, C g of not less than 0.95, C g 2 of not less than 0.40, an average major axis length of 40 to 5000 nm, and an aspect ratio (major axis diameter/minor axis diameter) of 1 to 200, to dispersing treatment; then subjecting the iron compound particles passed through a mesh screen to reducing treatment at a temperature of 160 to 420°C; and subjecting the resulting particles to nitridation treatment at a temperature of 130 to 170°C.