püsivmagnet

A püsivmagnet (Estonian for permanent magnet) is a material that produces a magnetic field without external power. Once magnetized, it retains much of its magnetization over long periods, although exposure to high temperatures, opposing magnetic fields, or mechanical shock can reduce its strength.

Permanent magnets are typically made from ferrites (ceramic magnets), alnico, samarium‑cobalt, or neodymium‑iron‑boron (NdFeB). These materials differ in remanence, coercivity, and temperature stability. The magnetic energy stored is described by the maximum energy product (BHmax), and the tendency to lose magnetization is measured by coercivity. All magnets have a Curie temperature above which magnetization is lost.

Common types have different tradeoffs: ferrite magnets are inexpensive and corrosion‑resistant; alnico magnets offer good temperature stability; samarium‑cobalt magnets provide strong resistance to demagnetization and high temperature performance; neodymium‑iron‑boron magnets deliver the highest magnetic strength but can require protective coatings and careful thermal management.

Applications include electric motors, generators, magnetic couplings and brakes, loudspeakers and headphones, sensors and encoders, latching devices, and magnetic separators. NdFeB magnets are widely used for high‑strength needs, while ferrites are common in cost‑effective gear.

Care and safety: magnets can pinch fingers and shatter if struck. Many magnets are coated to resist corrosion; high‑temperature operation can cause partial demagnetization. Proper handling and design considerations are necessary to avoid demagnetization and mechanical failure.