Ndfeb permanent magnet is known as the third-generation rare earth permanent magnet, which is the highest permanent magnet material ever. The main phase of sintered neodymium ferroboron alloy is metal intermetallic compound Nd2Fe14B, which is [1]. Because the sintered ndfeb permanent magnet alloy is composed of the main phase Nd2Fe14B and the grain boundary, and the grain orientation of Nd2Fe14B is limited by the technological conditions, the maximum residual magnetism of the magnet is 1.5t. The German vacuum smelting company (VacuumschmelzeGmbH) produces the maximum magnetic energy product (BH) Max, which reaches 57MGOe. The domestic neodymium tiboron manufacturer can produce the magnets of N50, and the highest magnetic energy can reach 53MGOe. The maximum magnetic energy of the magnet can be improved by increasing the ratio of the main phase of the alloy, increasing the orientation of grain and the density of the magnet. However, the theoretical value of the maximum magnetic energy product of single crystal Nd2Fe14B is not exceeded [1].

The demagnetization curve of neodymium iron boron is similar to that of a straight line. Therefore, when designing the permanent magnet motor, it is often used to select the high grade neodymium iron boron (i.e., the BH Max) to obtain high air gap magnetic density. When the motor is in operation, due to the existence of the alternating current of the magnetic field and the sudden change of load, the magnetic field effect of the instantaneous large current is required to select the neodymium ferroboron magnet which is high enough to be coercive.

In addition, the addition of dysprosium (terbium) and other elements in the alloy will increase the intrinsic coercivity (jHc) of the neodymium, but the magnetic remanence (Br) will decrease accordingly. Therefore, the high performance neodymium ferroboron magnetic steel used in wind turbines has both its coercivity and remanence.