Permanent magnets are objects that have been manufactured from a
magnetized material and are thus able to create their own persistent
magnetic field. As a whole, magnets can be largely broken up into two
categories: non-permanent and permanent. Non-permanent magnets are
electromagnets which require an external electric current to trigger
magnetism or non-magnetism. Permanent magnets, on the other hand, retain
their magnetism indefinitely or until they are demagnetized by
vibration, dirt, corrosion or interfering magnetic fields.
A magnet's capacity for retaining its magnetism under various conditions is called "magnetic permanence," and some types of permanent magnets have higher capacities for permanence than others. Typically, permanent magnets are fabricated from such chemical elements as non-rare earth elements like, alnico (aluminum-nickel-cobalt), ceramics (such as strontium and barium ferrite), and rare earth elements link, Sm-Co (samarium-cobalt) and NdFeB (neodymium-iron-boron). As an advantageous magnet option, permanent magnets are widely used in many industries, particularly for applications which require constant magnetic force, such as in metal separation and holding, as well as the automotive, industrial manufacturing, aerospace, construction industries and more. In addition to the aforementioned applications, another useful application is that mechanical motion can be created by permanent magnets when an electric current is introduced to one of the magnets' poles. However, rare earth magnets, including neodymium magnets and samarium cobalt magnets, have a much stronger magnetic force (and higher magnetic permanence) than other permanent magnets and for this reason can be used in small quantities to help with sound amplification and computer data processing. For instance, very small neodymium magnets help computer hard drives read and store information, or they may cause the vibration in speakers which produces sound. Ceramic magnets and aluminum-nickel-cobalt alloyed alnico magnets, two types of permanent magnet which are fabricated through sintering, are also used to amplify sound as well as for various metal holding, sorting and electric motor applications. This diversity of applications make permanent magnets essential in food processing, bulk material handling, metal fabrication and handling, electric motor manufacturing, sound amplification, data processing and many other industries. Magnet manufacturers can fabricate custom permanent magnets into a variety of shapes, densities and magnetic strengths.
Permanent Magnets - Master Magnetics, Inc.
Permanent Magnets - Magnum Magnetics Corporation