COBALT Magnets for Automotive Accessory Motors

The best COBALT magnets are of SmCo₅ type made by the powdered metallurgy-sintering process and provide energy products up to 160 kJ m³ (20 MGOe). Up to 90% of the samarium in SmCo₅ can be replaced by more plentiful rare earths, to produce magnets with energy products approximately 70% that of SmCo₅. This versatility allows motors to be optimized with respect to the availability of the various rare earths and the motor requirements. Bonded magnets are less brittle and can be machined but the magnetic properties and thermal stability are inferior to sintered magnets. Magnets can be laminated to powdered iron for improved toughness. COBALT magnets are available in small amounts from 22 magnet manufacturers and the starting material powders are produced by seven processors.