I. INTRODUCTION
The resource crisis of rare earth materials has broken
out in motor industry in the world. Rare earth material,
as the name shown, is “rare” in the globe. Nowadays,
many electric motors use rare earth permanent magnet
(PM). The efficiency of PM motors is high even in the
partial load condition or at the low speed operation.
Nd-Fe-B magnet is mainly used for such motors. High
efficiency and high power density can be easily realized
by using Nd-Fe-B magnet as rotating field magnet.
Almost all hybrid electric vehicles in the market use
several kilograms of Nd-Fe-B magnet in their traction
motor and generator. The number of HEV and EV are
growing rapidly near future.