Four main characteristics of powerful magnets

The magnetic energy when the magnetic moment of a powerful magnet is placed in the same direction as the external magnetic field will be lower than the magnetic energy when the magnetic moment is placed in the opposite direction to the external magnetic field. As a result, the magnetic domain with a small angle between the conscious magnetizing magnetic moment and the external magnetic field is in a favorable position. The volume of these magnetic domains gradually expands (domain wall displacement), and the volume of the magnetic domains whose self-magnetized magnetic moment is at a larger angle with the external magnetic field gradually decreases; when the external magnetic field is strong, the magnetic domain whose orientation is at a larger angle with the external magnetic field Gradually disappear, the remaining self-magnetized magnetic domains as a whole turn to the direction of the external magnetic field to varying degrees. This kind of material begins to show micromagnetism; when the external magnetic field reaches a certain value, all the magnetic domains turn to the direction of the external magnetic field. , the ferromagnet reaches a fully magnetized state, and its full magnetization intensity is equal to the original magnetization intensity in each magnetic domain, which is a large value.

There are four main characteristics of powerful magnets, which are mainly reflected in the following. The editor below will take you to learn more about them.

1. There is some kind of "conflict" between each magnetic domain that prevents each magnetic domain from returning to its original disordered demagnetization state after the external magnetic field is removed. Therefore, even if the external magnetic field is removed, ferromagnetic materials still retain some magnetism. When the external magnetic field is removed, the magnetization of a paramagnet immediately becomes zero. The relationship between magnetization and magnetic field strength is not linear, that is, the magnetic susceptibility and magnetic permeability are not constants, while the magnetic susceptibility and magnetic permeability of paramagnetic bodies are constant at a certain temperature.

2. It is easier to achieve magnetic saturation under the influence of an external magnetic field. At this time, the magnetization intensity no longer increases with the increase of the external magnetic field, but it is difficult for ordinary paramagnets to achieve magnetic saturation.

3. When the external magnetic field changes, the change in magnetization lags behind the change in the external magnetic field. This phenomenon is called the hysteresis effect. The hysteresis effect shows that the magnetization process of ferromagnets includes an obvious irreversible process. When the external magnetic field is removed, the ferromagnetic material still retains some magnetism, and its magnetization intensity is not zero, which is called residual magnetism. This is because there are factors such as doping in the ferromagnetic material.

4. There is a critical temperature TC. When the iron gas product is above TC, its ferromagnetism disappears and the ferromagnet transforms into a paramagnet. TC is called the Curie temperature or Curie point. Near the Curie temperature, the magnetic permeability and specific heat capacity increase abnormally.