RARE EARTH MAGNET POWDER AND METHOD FOR PRODUCTION THEREOF

摘要

A rare earth magnet powder which has a chemical composition that R: 5 to 20 % (wherein, R represents one or more of rare earth elements being exclusive of Dy and Tb and containing Y), one or two of Dy and Tb: 0.01 to 5 %, B: 3 to 20 %, and the balance: Fe and inevitable impurities, and has an average particle diameter of 10 to 1000 mum, wherein the rare earth magnet powder optionally further contains 0.1 to 50 % of Co and 0.001 to 5 % of M, and wherein 70 % or more of the surface of the rare earth magnet powder is covered with a layer being rich in the content of one or two of Dy and Tb and having a thickness of 0.05 to 50 mum, and the above Dy-Tb rich layer in a particle of the powder has such a concentration of one or two of Dy and Tb that the maximum detected intensity of the one or two of Dy and Tb in the layer, as measured by the wavelength dispersive X-ray spectroscopy, is 1.2 to 5.0 times the average detected intensity thereof in the central portion being present in the range of 1/3 of the diameter of the particle.