How can you restore a magnet’s strength?

28.9.2023

Why do magnets lose strength and how can you prevent it?

Magnets retain their strength for a very long time, but their magnetisation is not always completely permanent. Over time, temperature, mechanical damage or unsuitable conditions can lead to a loss of magnetic strength. In some cases, the loss can be reduced or the magnet can be partially restored.

You will learn why magnets gradually become weaker.
We will explain what is happening at the microstructural level.
We will show the main factors that affect resistance to demagnetisation.
We will also look at ways to protect and partially restore magnets.
We will add suitable products for home experiments and technical use.

Maintaining magnetic strength is very important for many applications. Whether it is a technical device, workshop use or working with magnets at home, it is always an advantage if a magnet retains its properties for as long as possible. Nevertheless, even a high-quality and strong magnet can lose part of its strength over time.

In this article, we will look at why this happens, what causes magnets to weaken and how this process can be partially prevented or at least slowed down.

Magnetisation and microstructure

To understand why magnets lose strength, we need to look at their microstructure. Magnetic strength arises from the way small magnetic units, often simply called magnetic dipoles, are arranged at the atomic level.

We can imagine the atoms inside a magnetic material as very small magnets. If these tiny magnetic moments are correctly aligned in the same direction, together they create a strong overall magnetic effect. This arrangement is the basis of how a magnet works.

A magnet is therefore essentially a collection of microscopic magnetic regions that work together to create the resulting magnetic force.

Simply put

A magnet is strong when its internal magnetic dipoles are aligned in the correct direction. Once this arrangement is disrupted, the magnetic strength begins to decrease.

Natural tendency towards demagnetisation

So why do magnets not remain equally strong forever? The reason lies in physical laws and the natural tendency of systems to move towards a more stable state. In a sense, a magnetised material represents a more ordered state that can gradually become disrupted over time.

The result is a slow transition to a less ordered state and therefore a gradual weakening of magnetic strength. In high-quality magnets, this process is usually very slow, but under certain conditions it can accelerate significantly.

Factors affecting resistance to demagnetisation

There are several main factors that determine how well a magnet retains its strength and how quickly it may weaken.

1. Time

Every magnet loses part of its magnetisation over time. This is usually a very slow process, and the loss is small in high-quality magnets. The rate of weakening also often slows down gradually.

2. Temperature

Temperature has a significant effect on magnetisation. At higher temperatures, magnets can lose strength more quickly. If the temperature exceeds a critical limit, part of the magnetic properties may be lost irreversibly.

3. Changes in reluctance

Reluctance is a physical quantity that expresses resistance to magnetic flux. If the magnetic circuit changes, for example if an air gap appears or the contact between the magnet and a metal surface changes, this can affect the magnet's behaviour and lead to weakening.

4. External magnetic fields

Strong external magnetic fields can change the orientation of magnetic dipoles inside the material and thereby cause partial or complete demagnetisation.

5. Mechanical damage

Drops, impacts or cracks can disrupt the internal structure of a magnet and reduce its effectiveness. This is especially true for more brittle magnetic materials such as neodymium magnets.

6. Radiation

In some specialised technical applications, radiation can also have an effect, particularly on selected types of magnets such as samarium-cobalt alloys.

How to protect magnets from weakening?

Although natural physical processes cannot be stopped completely, they can often be slowed down significantly by using and storing magnets appropriately.

Do not expose magnets to unnecessarily high temperatures.
Protect them from impacts and falls.
Do not leave them in unsuitable magnetic conditions for long periods.
Use magnets in the environment for which they are intended.
In humid environments, choose versions with suitable surface protection.

Can a weakened magnet be restored?

In some cases, yes. If the magnet has not lost too much strength and has not suffered serious damage, you can try to partially restore its effect. However, success depends on the type of material, the degree of weakening and the correct procedure.

Using another strong magnet

One option is to use another strong magnet. You can try placing the weakened magnet against a strong magnet and repeatedly moving it along its length. This can help the internal magnetic dipoles become better aligned in the correct direction again.

Using electric current

For electromagnets or magnetic cores, a higher electric current in the coil can help by creating a stronger magnetic field again and remagnetising the core.

Heating and remagnetisation

For some magnets, such as samarium-cobalt or neodymium magnets, controlled heating followed by cooling in a strong magnetic field can be used under specific conditions. However, this is a more specialised and technically demanding process.

Special magnetising equipment

There are also devices that generate very strong magnetic fields and are designed specifically for magnetising or remagnetising magnets. These are usually used in professional or industrial applications.

Important note

Not all magnets can be successfully restored. If the material has been permanently damaged or significantly demagnetised beyond a certain limit, returning to the original strength may not be possible.

When is it better to choose a new magnet?

If a magnet has lost too much of its strength, is mechanically damaged or no longer meets the required parameters, it is usually more practical to choose a new one. This is especially true when you need reliable performance, precise strength or long-term technical use.

In such a situation, it is worth choosing a suitable ferrite or neodymium magnet according to the specific application.

Not sure which magnet to choose as a replacement?

Ferrite magnets are suitable for everyday use and basic applications. If you need higher strength at a smaller size, neodymium magnets are usually a better choice.

Frequently asked questions about loss of magnetic strength

Do magnets lose strength on their own?

Yes, but usually very slowly. In high-quality magnets, the natural loss of magnetic strength is small and occurs over a long period of time.

What weakens magnets the most?

Most commonly high temperatures, mechanical damage, impacts, unsuitable storage and, in some cases, strong external magnetic fields.

Can a weakened magnet be strengthened again?

In some cases, yes. A strong magnet, electric current or a more specialised magnetising process may help. However, the result depends on the type of material and the extent of the damage.

How can you prevent a magnet from weakening quickly?

It is important to protect the magnet from heat, impacts, corrosion and unsuitable operating conditions. This can significantly extend its service life and stability.

When is it better to replace a magnet?

If the magnet no longer performs its function, is damaged or its strength remains insufficient even after an attempt at restoration, it is usually better to buy a new one with suitable parameters.

Summary

Magnets can retain their strength for a very long time, but they are not completely immune to time, temperature, impacts or unsuitable conditions. If a magnet weakens, in some cases it is possible to try to restore it partially. However, if the loss of strength is significant or permanent, the best solution is usually a suitably selected new magnet.

Looking for a replacement or stronger magnet?

Choose from ferrite and neodymium magnets for home use, school experiments and technical applications.

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