Sintered alnico magnets and cast alnico magnets are the two commercially available types of anisotropic alnico magnets. They are made in various ways and have varying magnetic properties when finished. Sintered anisotropic alnico magnets have an energy product range of 4.45-5.5 MGOe, whereas stronger cast anisotropic alnico magnets have an energy product range of 4.25-10 MGOe.
Anisotropic magnets have their magnetism direction permanently set during the manufacturing process, resulting in a stronger magnetic performance. Isotropic alnico magnets are also available in a limited number of cast and sintered grades. Isotropic alnico magnets are less commonly used because they have no preferred magnetism direction and thus are weaker, but they can be magnetised in different ways after manufacture, providing greater flexibility in magnetic circuit design.
Alnico magnets with magnetic lengths greater than their diameters, such as rod or bar shapes, are typically manufactured. Horseshoe-shaped magnets are traditionally made of alnico because they are effectively a bar magnet cast in a horseshoe shape, providing the greatest length-to-diameter ratio for the size of the magnet. Alnico magnets are prone to demagnetisation, which can be mitigated by increasing the length-to-diameter ratio.
