The magnetic energy when the magnetic moment of the strong magnet and the external magnetic field are placed in the same direction will be lower than the magnetic energy when the magnetic moment and the external magnetic field are placed in the opposite direction. The volume of these domains gradually expands (domain wall displacement), while the volume of the domains whose self-conscious magnetization moment and the external magnetic field become larger viewpoints gradually decrease.

When the external magnetic field is strong, the magnetic domains whose orientation is larger than that of the external magnetic field gradually disappear, and the remaining magnetic domains that have been consciously magnetized as a whole turn to the direction of the external magnetic field to varying degrees, and these substances begin to show microscopic magnetic properties. ; When the external magnetic field reaches a certain value, all the magnetic domains turn to the direction of the external magnetic field, and the ferromagnet reaches the full magnetization state, and its full magnetization is equal to the original magnetization in each magnetic domain, which is very large.






There are four main characteristics of strong magnets. There is a certain "conflict" between the magnetic domains to prevent the magnetic domains from returning to the original disordered demagnetization state after removing the external magnetic field. Therefore, even if the external magnetic field is removed, the ferromagnetic Still keeping some magnetic. When the paramagnet is removed from the external magnetic field, its magnetization becomes zero immediately. The relationship between the magnetization and the magnetic field is not linear, that is, the susceptibility and permeability are not constant, while the susceptibility and permeability of a paramagnet are constant at a certain temperature.

It is easier to reach the magnetic fullness under the effect of the external magnetic field. At this moment, the magnetization does not increase with the addition of the external magnetic field, and it is usually difficult for the paramagnet to reach the magnetic fullness. When the external magnetic field changes, the change of magnetization lags behind the change of the external magnetic field, which is called the hysteresis effect. The hysteresis effect indicates that the magnetization process of the ferromagnet contains an obvious irreversible process. When the external magnetic field is removed, the ferromagnet still retains some magnetism, and its magnetization is not zero, which is called remanence, which is due to the presence of doping and other
elements in the ferromagnetic substance.