What is coercivity (Hc)?

Once a magnet is magnetized, you want it to retain its magnetic properties. In practice, however, magnets are often exposed to influences that can reduce their magnetic force, such as high temperatures, strong external magnetic fields, or certain mechanical stresses.

The resistance a magnet offers to demagnetization is called coercivity.

Coercivity is one of the most important properties of a permanent magnet material and is usually denoted by the symbol Hc.

What does coercivity mean?

Coercivity indicates how much opposing magnetic force is needed for a magnet to lose its magnetization.

In other words:

the higher the coercivity, the harder it is to demagnetize a magnet.

A material with high coercivity retains its magnetic properties better under harsh conditions than a material with low coercivity.

Why is coercivity important?

In many applications, magnets are exposed to conditions that can affect their performance.

Consider, for example:

• electric motors
• generators
• industrial machinery
• sensors
• electric vehicles

If a magnet has insufficient coercivity, it may lose some of its magnetic force over time.

High coercivity helps prevent this.

Coercivity and neodymium magnets

One of the reasons why neodymium magnets are so popular in technical applications is their high coercivity.

This property ensures that they:

• remain stable for a long time
• are highly resistant to external magnetic influences
• are less susceptible to demagnetization

This allows them to be used in demanding industrial environments.

What is the difference between remanence and coercivity?

Remanence and coercivity are often mentioned together but describe different properties.

Remanence (Br) indicates how much magnetism a material possesses after the magnetizing field has been removed.

Coercivity (Hc) indicates how difficult it is to lose that magnetism again.

A simple comparison:

• Remanence tells how strong a magnet can be.
• Coercivity tells how well it remains strong.

Both properties are essential for high-quality permanent magnets.

How is coercivity measured?

Coercivity is usually expressed in:

• Amperes per meter (A/m)
• kiloamperes per meter (kA/m)
• Oersted (Oe)

Technical data sheets usually use one of these units.

The exact value depends on the material and magnet grade.

Coercivity and temperature

Temperature has a significant influence on coercivity.

When a magnet gets hotter, its resistance to demagnetization decreases.

Therefore, special neodymium grades exist, such as:

• H
• SH
• UH
• EH

These are developed to maintain sufficient coercivity even at higher temperatures.

Coercivity on the hysteresis curve

In materials science, coercivity is represented on the hysteresis curve.

The Hc value indicates how much opposing magnetic field is needed to reduce the net magnetization to zero.

Thus, coercivity is an important measure of the stability of a magnetic material.

Why is high coercivity important?

High coercivity offers advantages in applications where:

• high temperatures occur
• strong magnetic fields are present
• long-term stability is required
• reliability is essential

Therefore, coercivity plays an important role in the development of modern electric motors, generators, and industrial magnetic systems.

Conclusion

Coercivity (Hc) describes a magnet's resistance to demagnetization. The higher the coercivity, the harder it is to reduce a material's magnetic properties. Together with remanence and BHmax, coercivity is among the most important properties of permanent magnets and forms an essential parameter for technical applications.