Why the permanent magnet material demagnetization curve at any measurement point on the magnetic polarization strength J value and the magnetic induction B value must be less than the remanence Jr and Br value?

 

When the permanent magnetic material is magnetized in the closed state by external magnetic field to saturation, and then

the external magnetic field is canceled, the magnetic polarization J and the internal magnetic induction B of the permanent

magnetic material will not disappear due to disappearance of the external magnetic field H, The value of the material is

known as the residual magnetization of the material strength Jr and the residual magnetic flux density Br, collectively referred

to as remanence.

The units of remanence Jr and Br are the same as the units of magnetic polarization and magnetic induction.

 

When the magnetic field H is 0, Jr = Br, the magnetic field H is negative, J and B are not equal, then divided into two curves

of JH and BH, according to the relationship (1-1) . It can also be seen from the relation (1-1) that B changes from the maximum

value Br = Jr to 0 and finally to the negative value with the increase of the reverse magnetic field H. For the modern permanent

magnet material, the change of B demagnetization curve The law is often linear; J demagnetization curve of the variation is different:

with the increase of the reverse magnetic field H, B value decreases linearly, the value of B is always greater than or equal to the

reduction in the amount of increase in the reverse magnetic field H, So the J demagnetization curve in a certain area can maintain a

relatively straight line, but its J value is always less than Jr.