Ferrite magnets, sometimes referred to as ceramic because of their production process, are the least expensive class of permanent magnet materials. This material became commercially available in the mid-1950s, and has since found its way into countless applications including arc-shaped magnets for motors, magnetic chucks, and magnetic tools.
The raw material, iron oxide, for these magnets is mixed with either strontium or barium and milled down to a finely powdered form. The powder is then mixed with a ceramic binder and magnets are produced through a compression or extrusion molding technique that is followed by a sintering process. The nature of the manufacturing process results in a product that frequently contains imperfections such as cracks, porosity, chips, etc. Fortunately, these imperfections rarely interfere with a magnet’s performance.
To enhance a ceramic magnet’s performance, the ferrite compound may be biased by a magnetic field during the pressing process. This biasing induces a preferred direction of magnetization within the magnet, significantly reducing its performance in any other orientation. Consequently, ceramic magnets are available in both oriented (anisotropic) and non-oriented (isotropic) grades. Because of its lower magnetic properties, the isotropic grade of ferrite, ceramic 1, is typically utilized where complex magnetization patterns are required, and in process biasing would be cost prohibitive.
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