Hard ferrite magnets are produced with iron oxide and barium or strontium oxide. The raw materials are mixed together and normally pre sintered, to generate the magnetic phase. The pre sintered mixture then gets crushed. The resulting powder gets pressed together (wet or dry) either in a magnetic field (an – isotropic) or without a magnetic field (isotropic) and in the end sintered. Proceedings are only possible by grinding. Due to the low cost of the raw material, hard ferrite magnets are the cheapest magnet type out of the actual supply of magnets. Ferrites have a very good electrical isolation effect and are hard to demagnetize even in strong externalmagnetic fields. Corrosion tendency is low, this make this material suitable for applications in liquids.
Disadvantages are the high breakability and the low tensile strength. The strength and brittleness of hard ferrites are similar to ceramics. Furthermore the temperature resistance is limited and they have only a low energy to volume ratio.
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