Patent ID: 7297213

Claim:
A method for producing an iron-based rare earth alloy nanocomposite magnet including a hard magnetic phase and a soft magnetic phase, comprising the steps of: preparing a melt of a material alloy, the material alloy having a composition represented by the general formula: (Fe 1-m T m ) 100-x-y-z Q x R y M z , where T is at least one element selected from the group consisting of Co and Ni; Q is at least one element selected from the group consisting of B and C; R is at least one rare earth element substantially excluding La and Ce; and M is at least one metal element selected from the group consisting of Ti, Zr and Hf and always includes Ti, the mole fractions x, y, z and m meeting the inequalities of: 10 at %<x≦20 at %; 6 at %≦y<10 at %; 0.1 at %≦z≦12 at %; and 0≦m≦0.5, respectively; rapidly cooling the melt to make a rapidly solidified alloy comprising an R 2 Fe 14 B crystalline phase by: bringing the melt into contact with the surface of a rotating chill roller to obtain a supercooled liquid alloy; and dissipating heat from the supercooled alloy into the ambient gas to grow the R 2 Fe 14 B phase after the supercooled alloy has left the chill roller; and thermally treating the rapidly solidified alloy to form a structure in which two or more ferromagnetic crystalline phases, including the hard and the soft magnetic phases, exist, an average grain size of the hard magnetic phase is equal to or greater than 10 nm and equal to or less than 200 nm, and an average grain size of the soft magnetic phase is equal to or greater than 1 nm and equal to or less than 100 nm.