This guide focuses specifically on how hard ferrite (ceramic) permanent magnets are used in motors, speakers, sensors and other electronic or electromechanical assemblies. Ferrite is attractive when designers need an economical, corrosion-resistant permanent magnet and have enough space to work with its lower energy density compared with NdFeB.
Looking to buy ferrite magnets rather than research electronics applications? Browse Ceramic / Ferrite Magnets for stocked blocks, disks, rings and other available parts. For a broader material overview, use the Ferrite Magnets Properties & Selection Guide.
Hard Ferrite Magnets vs. Soft Ferrite Cores
The word “ferrite” is used for two related but different material families. Hard ferrite is permanently magnetized and is the material used in ceramic permanent magnets. Soft ferrite is designed to magnetize and demagnetize with an applied field and is commonly used in transformer cores, inductors and EMI components.
This article focuses on hard ferrite permanent magnets used as components in motors, speakers, sensors and mechanisms, not soft-ferrite electronic cores.
Why Ferrite Is Used in Electronic Products
- Low cost: ferrite works well in high-volume products where magnet cost matters.
- Good corrosion resistance: hard ferrite generally does not need protective nickel plating.
- Stable permanent magnet behavior: ferrite has good resistance to demagnetization when the magnetic circuit is designed correctly.
- Broad manufacturing availability: blocks, disks, rings and motor arc segments are common production forms.
Ferrite Magnets in Electric Motors
Ferrite magnets are widely used in motors for appliances, fans, pumps, blowers, automotive accessories and industrial equipment. They are especially attractive when the motor has enough space to accommodate a larger magnetic volume and the cost advantage of ferrite outweighs the size reduction possible with NdFeB.
For applications where compact size or higher torque density is critical, engineers may instead select neodymium. See Ferrite vs. Neodymium Magnets for the main design tradeoffs.
Ferrite Magnets in Speakers and Audio Equipment
Loudspeaker assemblies are another classic use of ferrite permanent magnets. A ceramic ring magnet works with the steel back plate, pole piece and top plate to concentrate magnetic flux into the narrow voice-coil gap. Current in the voice coil then interacts with that gap field to create the force that moves the cone.
Speaker performance is not determined by magnet diameter or magnet grade alone. The useful design target is the magnetic flux density in the voice-coil gap—and ultimately the motor force factor (Bl). Magnet volume, steel cross-section, gap width, pole geometry and saturation all affect how much of the ferrite magnet’s flux reaches the coil.
For the full loudspeaker design discussion, including ferrite vs. neodymium speaker motors, Bl, gap flux, steel saturation, thermal effects, shorting rings, tolerances and how to specify a speaker magnet, see Magnets for Speakers & Audio: Motor Design & Selection.
Is There a Standard Speaker Magnet Size Chart?
There is no universal speaker-magnet size chart that predicts driver output by magnet diameter alone. Two drivers using similar-size ferrite rings can have different gap flux and Bl because their pole pieces, top plates, gap widths and steel saturation levels are different. For OEM design, specify the required gap flux density or motor target together with the available magnet envelope rather than selecting only by outside diameter.
Ferrite Magnets in Sensors and Switches
Ferrite magnets can be used with Hall-effect sensors, reed switches and other position or proximity systems when the required field strength and air gap are compatible with ferrite. In tighter packages or applications requiring stronger fields at greater gaps, NdFeB may be more practical.
Other Electronic and Electromechanical Uses
- Magnetic latches and closures
- Small appliances and actuators
- General-purpose holding assemblies
- Educational and consumer products
- Low-cost magnetic couplings and mechanisms
When Ferrite Is Not the Best Choice
Ferrite is not ideal when the magnet must deliver very high force from a very small package. Because its energy density is much lower than NdFeB, changing from neodymium to ferrite often requires a larger magnet or a redesigned magnetic circuit.
If you are considering a material substitution, review Can Ferrite or Alnico Replace Neodymium?.
Source Ferrite Magnets for Motors, Speakers & Sensors
Radial Magnets stocks ceramic / ferrite blocks, disks and rings. For a loudspeaker or audio motor, start with the speaker magnet design guide to define the magnetic circuit and target gap flux. For custom dimensions, motor geometries, production quantities or special magnetization requirements, use the Magnet RFQ Builder. For multiple part numbers or annual-volume sourcing, use the Bulk Magnet RFQ.
