Permanent magnetic materials are also called "hard magnetic materials". A material that maintains constant magnetism once magnetized. It has wide hysteresis loop, high coercivity and high remanence.

Permanent magnetic materials are materials with wide hysteresis loop, high coercivity and high remanence, which can maintain constant magnetism once magnetized, also known as hard magnetic materials. The former is an intermetallic compound formed by rare earth elements cerium, praseodymium, lanthanum, neodymium and cobalt. Its magnetic energy product is 150 times that of carbon steel, 3 ~ 5 times that of Al Ni Co permanent magnet material and 8 ~ 10 times that of permanent ferrite. It has low temperature coefficient, stable magnetism and coercivity of 800 Ka / m. Rubber magnet is a kind of ferrite magnetic material series. It is a soft, elastic and twisted magnet made of bonded ferrite powder and synthetic rubber through extrusion molding, calendering molding, injection molding and other processes.

The magnetic property parameters of permanent magnet materials mainly include four parameters:

1) Residual magnetism Br (residual induction), unit: Gaussian, that is, the residual magnetic flux density after removing the magnetic field from the saturated state, which represents the strength of the magnetic field that the magnet can provide externally;

2) Coercivity HC (coercive force), unit: Auster oersteds, that is, put the magnet in a reverse applied magnetic field, and when the applied magnetic field increases to a certain strength, the magnetism of the magnet will disappear. This ability to resist the applied magnetic field is called coercivity, which represents the anti demagnetization ability of the magnet;

3) Intrinsic coercivity Hcj, unit: Auster oersteds, is a physical quantity to measure the anti demagnetization ability of magnet, and is the coercivity indicating that the magnetization m in the material retreats to zero. Different from the coercivity, when the reverse magnetic field H = BC, although the magnetic induction intensity B of the magnet is 0 and the magnet does not show magnetic flux, the vector sum of the micro magnetic dipole moment inside the magnet is often not 0, that is, at this time, the magnetic polarization intensity of the magnet often maintains a large value in the original direction. Therefore, HC is not enough to characterize the intrinsic magnetic properties of magnets; When the reverse magnetic field H increases to a certain value Hcj, the vector sum of the micro magnetic dipole moment in the magnet is 0, and the value of the reverse magnetic field H is called the intrinsic coercivity Hcj of the material.

4) The magnetic energy product BHmax, the unit Gauss oersteds, that is, the magnetic field energy generated by the unit volume material, is a physical quantity of the energy that the magnet can store.