What's the secialty of the material of the permanent magnets?

　   Once the materials of permanent magnets are magnetized by the external magnetic field , even in fairly large reverse magnetic field, they can still maintain a department or a large part of the original direction of magnetization of the magnetic.The requirements to such material is a high residual magnetic flux density Br, the coercive force, the magnetic energy product (BH) BHC. With respect to the soft magnetic material, it is also referred to as hard magnetic material.

　　The material of permanent magnets has alloy, ferrite and intermetallic compounds:

　　Alloy includes casting, sintering and processing of alloy. Casting alloy's main variety has: AlNi ( Co ), FeCr ( Co ), FeCrMo, FeAlC, FeCo ( V ) ( W. Sintered alloy has ReCo, ReFe and AlNi ( Co, FeCrCo ).Machinable alloy has: FeCrCo, PtCo, MnAlC, CuNiFe and AlMnAg, the latter two with lower BHCor is also called semi permanent magnetic material.

　　Intermetallic compounds are mainly represented by MnBi.