R-Fe-B-BASED FINE CRYSTAL HIGH-DENSITY MAGNET

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PROBLEM TO BE SOLVED : To provide a R-Fe-B-based fine crystal high-density magnet of which the magnetic characteristics do not deteriorate even when the size is as small as 3 mm or smaller. SOLUTION : The R-Fe-B-based fine crystal high-density magnet is a R-Fe-B-based fine crystal high-density magnet which is densified only by thermal energy without depending on a hot molding technique, and each has a structure in which a plurality of powder grains are bonded, which have aggregate structures of a Nd2Fe14B type crystal phase having an average crystal grain size of 0.01 μm or larger but 2 μm or smaller. The magnet has the powder grains with an average grain size of smaller than 20 μm, satisfies relationships of 10 atom%≤R≤30 atom% and 3 atom%≤Q≤15 atom% when R is a composition ratio of rare earth elements and Q is a composition ratio of boron (composition ratio of boron and carbon when carbon is added thereto), and has the density of 93% or more of the real density. A rare earth rich phase exists in a region located among the powder grains. The number density of the rare earth rich phase is 1.6×104 pieces/mm2 or more in a cross section passing the center part of the magnet when the area of the cross section is 1 μm2 or more but 10 μm2 or less. COPYRIGHT : (C)2012, JPO&INPIT