Method for producing rare earth magnets, and rare earth magnets

A rare earth magnet that is represented by the following composition formula:

• RvFewCoxByMz,
• wherein R is one or more kinds of rare earth elements including Y,
• M is at least one kind of Ga, Zn, Si, Al, Nb, Zr, Ni, Cu, Cr, Hf, Mo, P, C, Mg, V, Hg, Ag and Au,
• 13≦v≦20,
• w=100-v-x-y-z,
• 0≦x≦30,
• 4≦y≦20, and
• O≦z≦3.
• wherein the rare earth magnet is constituted of either one of the following (i) and (ii):
• (i) a main phase R2(FeCo)14B, and a grain boundary phase R(FeCo)4B4 and R, and
• (ii) a main phase R2(FeCo)14B, and a grain boundary phase R2(FeCo)17 and R;
• and
• wherein a minimum value of an atomic ratio of Fe to Nd in the grain boundary phase when analyzed by energy dispersive X-ray spectrometry is 1.00 or less.

A rare earth magnet that is represented by the following composition formula:

• RvFewCoxByMz,
• wherein R is one or more kinds of rare earth elements including Y,
• M is at least one kind of Ga, Zn, Si, Al, Nb, Zr, Ni, Cu, Cr, Hf, Mo, P, C, Mg, V, Hg, Ag and Au,
• 13≦v≦20,
• w=100-v-x-y-z,
• 0≦x≦30,
• 4≦y≦20, and
• 0≦z≦3,
• wherein the rare earth magnet is constituted of either one of the following (i) and (ii):
• (i) a main phase Nd2Fe14B, and a grain boundary phase R(FeCo)4B4 and R, and
• (ii) a main phase Nd2Fe14B, and a grain boundary phase R2(FeCo)17 and R;
• and
• wherein a minimum value of an atomic ratio of Fe to Nd in the grain boundary phase when analyzed by energy dispersive X-ray spectrometry is 1.00 or less.

A production method of a nanocrystalline rare earth magnet having a grain and a grain boundary phase comprising:

• quenching a melt of a rare earth magnet composition to form a quenched thin ribbon having a nanocrystalline structure;
• sintering the quenched thin ribbon to obtain a sintered body;
• applying an alignment treatment to the sintered body;
• after the alignment treatment was applied, heat treating the sintered body at a heat treatment temperature which is higher than a lowest temperature in a first temperature range where the grain boundary phase diffuses or flows, and which is lower than a lowest temperature in a second temperature range where the grain becomes coarse;
• and
• quenching the heat treated sintered body to 200° C. or less at a cooling speed of 50° C./min or more.