Study of the coercivity enhance mechanism of Nd-Fe-B type permanent magnets using multiscale structural analysis

摘要

The Nd-Fe-B type permanent magnets, which exhibit excellent hard magnetic properties, were discovered about 25 years ago. Since that time, many researchers have been working to improve hard magnetic properties of these magnets. The Nd-Fe-B type permanent magnets are widely used in different application specifically electro-mechanical applications in different types of motors. However, the coercivity of the Nd-Fe-B sintered magnets (～10 kOe) is only 14% of the anisotropy field (～75 kOe), which is too low for certain applications such as traction motors for hybrid and electric vehicles. The current Nd-Fe-B high coercivity sintered magnets for hybrid and electric vehicle applications contain Dy (approximately 40% of total rare earth elements) to increase the coercivity to the level of 30 kOe, However, due to high cost and limited natural resources for Dy, developing high coercivity Nd-Fe-B permanent magnets without using Dy became the center of current research interest all over the world.