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 available. Hard ferrite magnets have very good electrical isolation effects and are hard to demagnetize even in strong external magnetic fields. Corrosion tendency is low, making them very suitable for liquid applications. 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.
