Permanent magnets: The unshakeable powerhouses of magnetism

A permanent magnet is a magnet that generates a permanent magnetic field without external influences. It consists of materials whose magnetic domains are permanently aligned through special production and magnetisation. This property distinguishes it from electromagnets, which only generate a magnetic field when active.

Properties of a permanent magnet

• Permanent magnetisation: Permanent magnets retain their magnetisation over a long period of time, even without an external magnetic field.
• High coercivity: They resist external demagnetisation fields thanks to their stable magnetic structure.
• Resistant to corrosion: Many permanent magnets are provided with a protective coating such as nickel, epoxy or zinc.

Typical materials for permanent magnets

• Neodymium-iron-boron (NdFeB): These magnets offer the highest magnetic performance and are used in modern applications such as electric motors, loudspeakers and wind turbines.
• Ferrite: Cost-effective and corrosion-resistant, ideal for everyday applications such as refrigerator magnets or loudspeakers.
• Samarium-Cobalt (SmCo): High temperature resistance, ideal for high-temperature applications such as in aviation or industry.
• AlNiCo: An alloy of aluminium, nickel and cobalt, known for its high temperature stability but lower magnetic performance.

Application areas

Permanent magnets are used in a variety of applications:

• Electric motors: Permanent magnets generate the magnetic field that drives the movement of the motor.
• Sensors: Precise magnetic fields in sensors enable the measurement of position, speed or current flow.
• Holding magnets: Magnets in furniture, fastening systems or tool holders are based on the adhesive force of permanent magnets.
• Electronics: Loudspeakers, microphones and headphones use the constant magnetisation of permanent magnets.

Special features

An important factor for permanent magnets is the maximum operating temperature, which varies depending on the material:

• Neodymium: approx. 80-200 °C
• Ferrite: approx. 250 °C
• Samarium-cobalt: up to 350 °C

Did you know?

Permanent magnets can lose their magnetisation over time due to high temperatures, strong vibrations or extremely strong external magnetic fields. Modern technologies such as protective coatings and alloys significantly improve their longevity.