permanentmagneter

Permanent magnets, or Permanentmagneter in Swedish, are materials that produce a persistent magnetic field without an external energy source. The magnetization arises from aligned magnetic domains within the material, and a permanent magnet can retain most of its magnetization when the external field is removed. Key properties include a remanent flux density, coercivity, and the maximum energy product (BH max).

Common permanent magnet materials are ferrites (ceramic magnets), alnico alloys, neodymium-iron-boron (NdFeB), and samarium-cobalt (SmCo). Ferrites are inexpensive and corrosion-resistant but have lower energy density. Alnico offers good temperature stability and magnetization strength but lower resistance to demagnetization. NdFeB magnets deliver the highest energy density but are prone to corrosion and demagnetization at high temperatures, usually requiring coatings. SmCo magnets provide strong resistance to demagnetization and high temperature tolerance, at higher cost and brittleness.

The Curie temperature varies by material, typically around 310°C for NdFeB and about 350°C for SmCo; ferrites tolerate higher temperatures in some cases. In manufacturing, magnets are produced by casting or sintering (most NdFeB, SmCo, and ferrites) or bonding, then magnetized along a chosen axis.

Applications include electric motors and generators, loudspeakers and headphones, magnetic separation, and various sensors. Handling requires care to avoid injury or damage from strong attraction and to prevent magnetic loss; magnets can be demagnetized by heat, strong opposing fields, or physical shock. Environmental considerations include the sourcing and recycling of rare-earth elements used in modern magnets.