Square property and excellent thermal stability and a rare earth magnet-Fe-Co-B magnet powder

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PROBLEM TO BE SOLVED : To provide R-Fe-Co-B magnet powder having superior squareness and thermostability, and a bonded magnet using the powder. SOLUTION : Rare-earth-Fe-Co-B magnet power has a composition containing 10-20% R, 0.1-50% Co, 3-20% B, 0.01-2.0% one or two or more kinds of elements selected from among Al, V, and Si, 0.01-5.0% Cr, Mo, or Cr and Mo, 0.001-5.0% one or two or more kinds of elements selected from among Ga, Zr, and Hf as necessary, and the balance Fe with traces of unavoidable impurities, a recrystallized-grain aggregate structure constructed by adjacently aggregating recrystallized grains, having main phases composed of R2 (Fe, Co)14B type intermetallic compound phases. In the aggregate structure, the average particle diameter of the recrystallized grains constituting the aggregate structure is adjusted to 0.05-3 μm and the occupying volume of such recrystallized grains that the ratio (b/a) of their longest diameter (b) to their shortest diameter (c) are adjusted to be 50% or larger of the occupying volume of all recrystallized grains.