Why don't magnets lose their magnetism at some point?

Right / magnet: Does a magnet lose its power over time?

Jacek Krzywinski, physicist and developer at Magnetfabrik Bonn, has had a magnet made of the metal neodymium in the basement for 20 years. "It is a little rusty on the surface, but it has retained its strength." Krzywinski describes three enemies of the permanent magnet: first, decomposition, for example through oxidation; second, high temperatures; and third, external magnetic fields. If you protect your magnet from these influences, you can enjoy it practically unlimited.

The phenomenon of magnetism is physically quite complicated and can ultimately only be explained with the subtleties of quantum theory. For our purposes, it is important to distinguish between magnetizable materials, which can be used to make permanent magnets, and others that are temporarily turned into magnets, such as electromagnets. Permanent magnets can only be made from the metals iron, nickel and cobalt and their alloys.

You won't find modern magnets anywhere in nature. To make them, these three metals are exposed to a strong magnetic field. Then the "elementary magnets" that make up the material all orient themselves in the same direction. This orientation remains when the external magnetic field is no longer there.

The question is: can this orientation be lost again over time? This is known, for example, from steel tools that can accept a weak magnetic field and then attract small metal parts, for example. This weak magnetization can even be lost again by a strong mechanical shock.

Strong commercial magnets are not so easily disoriented. Most of all, heat can cause them problems. Every magnetic material has a so-called Curie temperature at which the magnetization is lost. In practice, a weakening can occur even at lower temperatures. The super-strong magnets made of neodymium compounds are particularly sensitive - a temperature of 80 degrees Celsius can weaken them noticeably. But magnets are also troubled by extreme cold.



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As long as the metal has not chemically decomposed, the loss of magnetization is reversible: you just have to expose it to a strong external magnetic field again and it will regain its forces.