Nanocomposite magnet powder and method for producing the magnet

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The inventive method for preparing nanocomposite magnet powder includes the step of preparing material alloy powder for a nanocomposite magnet represented by a general formula Fe100-x-y-z-uRxByCozMu where R is a rare-earth element of which 90-100 atomic percent is Pr and/or Nd while 0-10 atomic percent is another lanthanoid and/or Y, and the molar fractions x, y, z and u meet the inequalities of 2<=x<=6, 16<=y<=20, 0.2<=z<=7 and 0.01<=u<=7, respectively. The powder includes a metastable phase and an amorphous structure existing in a metal structure. Heat treatment is performed for the material alloy powder to crystallize Fe3B and Fe-R-B compounds from the amorphous structure. An integral value of the difference between a temperature-time curve represented by the temperature of the material alloy powder as a function of the heat treatment time during the heat treatment and a reference temperature-time curve is in a range from 10° C..sec to 10, 000° C..sec, the reference temperature-time curve being obtained when heat treatment similar to the above heat treatment is performed for an equivalent amount of alloy that has the same composition as the material alloy but does not include the amorphous structure.