Are permanent magnets really permanent?

A permanent magnet is a material that can maintain its magnetism for a long time without relying on an external power source. Common permanent magnets include ferrite, NdFeB, AlNiCo alloy, etc. Although the name "permanent magnet" gives people the impression that its magnetism is "permanent", in fact, the magnetism of a permanent magnet is not absolutely permanent, but will gradually decay with time and changes in external conditions.

Temperature is an important factor affecting the magnetism of a permanent magnet. Each permanent magnet material has a specific "Curie temperature", above which the magnetism of the material will be lost. For example, the Curie temperature of a NdFeB permanent magnet is about 310°C. Above this temperature, the NdFeB material will lose its magnetism. In addition, even at room temperature, if a permanent magnet is exposed to a high temperature environment for a long time, its magnetism will be affected and gradually decay.

The effect of an external magnetic field will also affect the magnetism of a permanent magnet. If a permanent magnet is in a strong external magnetic field, especially when the direction of the external magnetic field is opposite to that of the permanent magnet, the magnetism of the permanent magnet may weaken or even reverse magnetization may occur. In addition, mechanical shock is also one of the factors that cause permanent magnets to degrade. If a permanent magnet is subjected to severe shock or vibration, its internal crystal structure may be destroyed, resulting in weakened magnetism.

In addition to external factors, the magnetic decay of permanent magnets is usually a process that occurs slowly over time. The speed of this process is closely related to the material properties of the permanent magnet. Permanent magnets of different materials have different rates of magnetic decay. For example, neodymium iron boron (NdFeB) permanent magnets have strong magnetism, but their magnetism may decay faster than that of ferrite materials in long-term use.

Although the magnetism of permanent magnets is not absolutely permanent, many permanent magnets can maintain their magnetism for decades or even longer under proper conditions of use. In order to extend the service life of permanent magnets, some protective measures are usually taken, such as avoiding high temperatures, strong shocks and vibrations, etc.

Reiner hochwertiger industrieller Neodym-Magnet