Method for preparing nanocomposite magnet powder and method for producing nanocomposite magnet

A method for producing a nanocomposite magnet, said method comprising the steps of:

• preparing material alloy powder for a nanocomposite magnet, said powder being represented by a general formula Fe100−x−yRxBy, Fe100−x−y−zRxByCoz, Fe100−xy−uRxByMu or Fe100−x−y−z−uRxByCozMu, where R is a rare-earth element;
• 78-100 atomic percent of R is Pr and/or Nd, 0-22 atomic percent of R is another lanthanoid and/or Y;
• M is at least one element selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Ni, Cu, Ga, Zr, Nb, Mo, Hf, Ta, W, Pt, Pb, Au and Ag;
• 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, said powder including a metastable phase and an amorphous structure existing in a metal structure;
• heat-treating said material alloy powder for the nanocomposite magnet to crystallize Fe3B and Fe—R—B compounds;
• and
• molding said heat-treated material alloy powder,
• wherein an integral value of the difference between a temperature-time curve represented by the temperature of said material alloy powder for the nanocomposite magnet and the heat treatment time in the step of heat-treating the material alloy powder for the nanocomposite magnet 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 by heat-treating said material alloy powder for the nanocomposite magnet for an equivalent amount of alloy that has the same composition as said material alloy for the nanocomposite magnet but does not include said amorphous structure.