- Last updated: August 22, 2023
Coercivity measures permanent magnet stability.
This beginner’s guide explains what coercivity is.
Learn how it resists demagnetization.
Discover how to compare magnets based on it.
If you’re new to coercivity, start here.
Let’s dive into this key concept!
Introduction to Magnetism
Before exploring coercivity, let’s briefly discuss magnetism and some key terms related to it.
What is a Magnet?
A magnet is an object that generates a magnetic field, attracting or repelling certain materials, such as iron, nickel, and cobalt. Magnets come in various shapes, sizes, and strengths, and are used in a wide range of applications, from everyday household items to complex industrial machinery.
Permanent vs. Temporary Magnets
Permanent magnets are materials that retain their magnetic properties even when they are not subjected to an external magnetic field. Temporary magnets, on the other hand, exhibit magnetic properties only when exposed to an external magnetic field and lose these properties once the field is removed.
Understanding Coercivity
Now that we have a basic understanding of magnets, let’s delve into the concept of coercivity.
Definition
Coercivity is a measure of a magnet’s resistance to demagnetization. It is defined as the intensity of the external magnetic field required to reduce the magnetization of a magnet to zero after it has been magnetized to saturation. Coercivity is typically measured in units called oersteds (Oe) or amperes per meter (A/m).
Types of Coercivity
There are two types of coercivity: intrinsic coercivity and coercive force. Intrinsic coercivity (Hci) refers to the resistance of a magnet’s material to demagnetization, whereas coercive force (Hc) represents the actual resistance of a magnet to demagnetization, taking into account factors such as shape and size.
Factors Affecting Coercivity
Several factors influence a magnet’s coercivity, including its material composition, size, shape, and temperature. Generally, magnets with higher coercivity are more resistant to demagnetization, making them suitable for applications where they may be exposed to strong external magnetic fields or high temperatures.
Why You Should Care
Understanding coercivity is essential when selecting magnets for different applications. Here’s why:
Magnet Stability
Coercivity affects a magnet’s ability to maintain its magnetic properties over time. Magnets with higher coercivity are more stable and less likely to lose their magnetism due to external factors such as temperature changes or exposure to other magnetic fields.
Demagnetization Resistance
A magnet’s coercivity helps determine its resistance to demagnetization. Magnets with higher coercivity values are less likely to become demagnetized when exposed to external magnetic fields or elevated temperatures, ensuring optimal performance and longevity.
Application Suitability
Coercivity can help you choose the right magnet for specific applications, particularly those with varying temperature or magnetic field conditions. By understanding a magnet’s coercivity, you can ensure that it will perform well and maintain its magnetic properties under the expected operating conditions.
Measuring Coercivity
To determine a magnet’s coercivity, specialized equipment is required.
Hysteresis Loop
A hysteresis loop is a graphical representation of the relationship between a magnet’s magnetization and the applied magnetic field. Coercivity is determined from the hysteresis loop as the point where the magnetization curve intersects the magnetic field axis. This point represents the strength of the external magnetic field required to demagnetize the magnet completely.
Magnetometers
Magnetometers are devices used to measure the magnetic properties of materials, including coercivity. They typically employ a technique called vibrating sample magnetometry (VSM) or alternating gradient magnetometry (AGM) to generate hysteresis loops and determine a magnet’s coercivity.
Using Coercivity to Choose the Right Magnet
Now that we understand the basics of coercivity, let’s explore some practical tips for using it to select the appropriate magnet for various applications.
Assessing Your Application Requirements
To choose the right magnet, first consider the coercivity requirements for your specific application. Think about factors such as the desired force, operating temperature, and any potential interference with other electronic devices or magnetic fields.
Comparing Magnets Based on Coercivity
When comparing different magnets, consider their coercivity values as an essential factor. Higher coercivity usually indicates better resistance to demagnetization and more stable performance. However, other properties, such as size, shape, and material, can also affect overall magnet performance and should be taken into account.
Considering Temperature and External Magnetic Fields
Be sure to account for temperature and external magnetic field variations when choosing a magnet based on coercivity. Select a magnet that can maintain its coercivity and overall performance under the expected operating conditions for your application.
Conclusion
You now have an overview of magnet coercivity.
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