Samarium Colbalt Magnets
Sintered samarium cobalt (SmCo) magnets, available since the early 1970, offer the designer a tremendous combination of extremely high magnetic properties, outstanding thermal stability and excellent corrosion resistance. These characteristics make SmCo the ideal material in applications such as servo-motors, pump couplings, and sensors, particularly where the magnet is required to operate at high temperatures, across a broad temperature range or in a corrosive environment.
Maximum Operating Temperature
Although the Curie temperature for SmCo material is between 700 and 800 ºC, currently alloy compositions can only be used up to maximum temperature between 250 and 350 ºC. Major efforts are underway in the industry to raise the maximum use temperature above 400 ºC. Compare this with NdFeB’s maximum operating temperature of 150 ºC to 200 ºC. Other advantages of SmCo over NdFeB include better corrosion resistance and greater magnetic output at temperatures above about 150ºC.
Sensor applications requiring a stable magnetic field benefit from SmCo’s low reversible temperature coefficient of induction: -0.030%/ºC for Sm2Co17. The best NdFeB varies more than twice as much. The only common material with a lower coefficient than this is alnico, but with significantly low magnetic energy products.