What is the demagnetization curve of a disc magnet?

Hey there! As a disc magnet supplier, I often get asked about the demagnetization curve of disc magnets. So, I thought I'd write this blog to explain it in a simple and easy - to - understand way.

First off, let's talk about what a disc magnet is. Disc magnets are those flat, circular magnets that you can find in all sorts of sizes. For example, we have the 6x2mm Disc Magnet and 5x3mm Neodymium Magnets. These little guys are used in tons of applications, from small electronic devices to industrial machinery.

Now, onto the demagnetization curve. The demagnetization curve is basically a graph that shows how a magnet's magnetic properties change when it's exposed to an external magnetic field or other demagnetizing factors. It's super important because it helps us understand how strong a magnet will remain under different conditions.

Understanding the Basics of the Demagnetization Curve

The demagnetization curve is plotted with two main axes. On the horizontal axis, we have the magnetic field strength (usually denoted as H), and on the vertical axis, we have the magnetic flux density (denoted as B).

When a magnet is in its normal, fully magnetized state, it has a certain level of magnetic flux density. But as we start applying an external magnetic field in the opposite direction (a demagnetizing field), the magnetic flux density starts to decrease. The demagnetization curve shows this relationship between the applied demagnetizing field and the resulting magnetic flux density of the magnet.

There are a few key points on the demagnetization curve that we need to know about. The first one is the remanence (Br). This is the magnetic flux density that remains in the magnet when the external magnetic field is removed after the magnet has been fully magnetized. In simpler terms, it's how strong the magnet is on its own, without any external help.

Another important point is the coercivity (Hc). This is the amount of external magnetic field that needs to be applied in the opposite direction to completely demagnetize the magnet. It's a measure of how resistant the magnet is to being demagnetized. The higher the coercivity, the harder it is to demagnetize the magnet.

Types of Demagnetization Curves

Not all demagnetization curves are the same. Different types of magnets have different shapes of demagnetization curves, and this depends on the material they're made of.

Neodymium Disc Magnets

Neodymium disc magnets, like the ones we supply at our company, have a very distinct demagnetization curve. They are known for their high remanence and high coercivity. This means they are very strong magnets and are quite resistant to demagnetization. The demagnetization curve for neodymium magnets is relatively straight in the initial part, which indicates that they can maintain a high magnetic flux density even when exposed to a moderate demagnetizing field.

Ferrite Disc Magnets

Ferrite disc magnets, on the other hand, have a different demagnetization curve. They have a lower remanence and coercivity compared to neodymium magnets. Their demagnetization curve is more rounded, which means they start losing their magnetic properties more gradually when exposed to a demagnetizing field.

Factors Affecting the Demagnetization Curve

There are several factors that can affect the demagnetization curve of a disc magnet.

Temperature

Temperature is a major factor. As the temperature of a magnet increases, its magnetic properties start to degrade. The demagnetization curve shifts downwards as the temperature rises, which means that the remanence and coercivity both decrease. For example, neodymium magnets can lose a significant amount of their magnetic strength at high temperatures. That's why in applications where high - temperature stability is required, we might need to use special high - temperature - resistant neodymium magnets or other types of magnets.

Mechanical Stress

Mechanical stress can also have an impact on the demagnetization curve. If a magnet is subjected to physical forces like bending, crushing, or vibration, it can cause internal changes in the magnet's structure, which in turn can affect its magnetic properties. This can lead to a shift in the demagnetization curve and a decrease in the magnet's overall strength.

External Magnetic Fields

As we mentioned earlier, external magnetic fields are the main cause of demagnetization. If a magnet is placed in an environment where there are strong external magnetic fields, especially in the opposite direction to its own magnetic field, it can start to lose its magnetic strength. The demagnetization curve helps us predict how much the magnet will be affected by these external fields.

Why the Demagnetization Curve Matters for Disc Magnet Applications

The demagnetization curve is crucial for a wide range of applications that use disc magnets.

In Electric Motors

In electric motors, disc magnets are used to create the magnetic field that drives the rotation of the motor. The demagnetization curve helps engineers design motors that can operate efficiently under different conditions. For example, if a motor is going to be used in an environment with high temperatures or strong external magnetic fields, they need to choose a magnet with a demagnetization curve that can withstand these conditions. Otherwise, the motor might lose its power over time.

In Magnetic Sensors

Magnetic sensors rely on the stable magnetic properties of disc magnets. The demagnetization curve helps sensor designers ensure that the magnets used in the sensors will maintain their accuracy and reliability. If the magnet's magnetic properties change due to demagnetization, the sensor might give inaccurate readings.

How We Use the Demagnetization Curve in Our Business

As a disc magnet supplier, we use the demagnetization curve in several ways.

Quality Control

We use the demagnetization curve as a part of our quality control process. By testing the demagnetization characteristics of our magnets, we can ensure that they meet the required standards. We measure the remanence and coercivity of each batch of magnets and compare them to the expected values based on the demagnetization curve. If the values are outside the acceptable range, we know that there might be a problem with the manufacturing process or the raw materials.

Product Selection

When customers come to us looking for disc magnets for their specific applications, we use the demagnetization curve to recommend the right type of magnet. For example, if a customer needs a magnet for a high - temperature application, we'll look for magnets with a demagnetization curve that shows good stability at high temperatures.

Conclusion

So, there you have it! The demagnetization curve is a vital tool for understanding the behavior of disc magnets. It helps us predict how a magnet will perform under different conditions, and it plays a huge role in the design and application of magnets in various industries.

If you're in the market for disc magnets, whether it's the 6x2mm Disc Magnet, 5x3mm Neodymium Magnets, or any other type, we're here to help. We have a wide range of Disc Magnets to meet your needs. If you have any questions about the demagnetization curve or which magnet is right for your application, don't hesitate to reach out to us. We're always happy to have a chat and help you find the perfect magnet for your project.

References

• Handbook of Magnetic Materials
• Magnetics: Principles and Applications textbook