Ceramic Magnets:
(Hard Ferrite) are composed of barium or strontium, which were developed in the early 1960s as an alternative to the more expensive metallic magnets. This class of magnet is very hard, brittle and possesses lower energy characteristics compared to other magnetic materials. However, it is very popular and widely used because of its excellent resistance to demagnetisation, corrosion, and advantageous pricing.
Ferrite magnets are manufactured by pressing, sintering, or injection moulding. These magnets can be both anisotropic and isotropic. Anisotropic grades are oriented during the manufacturing process and must be magnetised in the direction of orientation. Isotropic grades are not oriented and can be magnetised in any direction.
Applications of Ceramic Magnets
- Speaker Magnets
- DC brushless motors
- Magnetic Resonance Imaging (MRI)
- Magnetos used on lawnmowers and outboard motors
- DC permanent magnet motors (used in cars)
- Separators (separate ferrous material from non-ferrous)
- Used in magnetic assemblies for lifting, holding, retrieving and separating
Alnico has a low coercive force and is easily demagnetized if not handled with care. For optimum performance of Alnico 5, the magnetic length should be approximately 5 times the pole diameter or equivalent diameter. For example, a 0.250" diameter magnet should be about 1.00" long.
Because of its higher coercivity, Alnico 8 may be used in shorter lengths and disc shapes.