Alnico magnets are among the most stable permanent magnets available today. Composed primarily of aluminum (Al), nickel (Ni), and cobalt (Co)—along with iron and other elements—Alnico magnets offer excellent temperature stability, high residual induction, and long-term magnetic performance. However, under certain conditions, even these robust magnets can be demagnetized.
In this article, we’ll explain the most common methods used to demagnetize Alnico magnets and how demagnetizer machines work—critical information for engineers, designers, and anyone working with magnetic assemblies.
Why Would You Need to Demagnetize an Alnico Magnet?
There are a few reasons for intentional demagnetization:
- Resetting the magnetic state for remanent magnetization measurements
- Deactivating magnetic fields in finished assemblies
- Recycling or reusing magnetic materials
- Troubleshooting field interference in sensitive devices
Understanding how to safely and effectively demagnetize Alnico magnets is crucial in these cases.
Methods for Demagnetizing Alnico Magnets
1. AC Demagnetization (Alternating Current Field)
This is the most controlled and widely used method for demagnetizing Alnico magnets. The magnet is exposed to a strong alternating magnetic field that gradually reduces in intensity.
The AC field randomizes the orientation of magnetic domains, effectively neutralizing the magnet’s net field. A typical demagnetizer machine used for this process delivers up to 350 kA/m of alternating magnetic field strength.
2. Thermal Demagnetization
Alnico magnets can also be demagnetized by heating them beyond their Curie temperature (around 800°C). At this temperature, the aligned domains lose their magnetic orientation.
However, thermal demagnetization can permanently alter the material’s microstructure, especially in precision applications, so this method is used with caution.
3. Mechanical Shock
A less controlled approach, mechanical stress—such as dropping or striking a magnet—can partially demagnetize it. This method is generally discouraged due to the risk of damage and poor repeatability.
How Do Demagnetizers Work?
A demagnetizer, also known as a degausser, generates a high-frequency alternating magnetic field. The field interacts with the magnetized object, progressively scrambling its magnetic domains until no net magnetism remains.
Some types of demagnetizers include:
- Tabletop demagnetizers for small parts
- Tunnel demagnetizers for bulk or inline processing
- Custom AC coils for large Alnico assemblies
Alnico Demagnetization vs. Other Magnet Types
Alnico magnets are unique because they have:
- High coercivity at room temperature
- Lower resistance to demagnetizing fields compared to rare earth magnets
- Excellent temperature stability for critical applications
This means that while Alnico is resistant to everyday magnetic interference, it can still be intentionally demagnetized using proper techniques—especially AC field demagnetizers.
We Manufacture Custom Alnico Magnets for Any Application
At HS Magnetics, we specialize in designing and manufacturing Alnico magnets tailored for a wide range of industries, including:
- Sensors and instrumentation
- Magnetic assemblies
- Audio equipment
- Automotive and aerospace
Whether you need precision-cast Alnico magnets or high-performance sintered Alnico components, we offer cost-effective solutions with consistent quality.
Final Thoughts
Understanding how Alnico magnets are demagnetized is essential for engineers and product designers who depend on predictable magnetic behavior. AC demagnetization is the most reliable and efficient method, and it’s commonly used in precision applications.
If you’re looking for a trusted Alnico magnet manufacturer, HS Magnetics is here to help—from raw material selection to post-processing support, including demagnetization guidance.