Sintered samarium cobalt (SmCo) magnets, 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.

The first alloy composition was SmCo5 with maximum energy products of about 18 MGOe (140 kJ/m3). Shortly after this development, an additional alloy composition, Sm2Co17 was developed by Karl Strnat. This was developed over time to provide over 30 MGOe (240 kJ/m3). Although processing of the 2-17 composition is more difficult, it also has the advantage of containing less Cobalt than the 1-5 composition. Raw material costs are lower. 2-17 is also more corrosion resistant and more stable at very high temperatures.

Although the Curie temperature for SmCo materials is between 700 and 800 degrees, current alloy compositions can only be used up to maximum temperatures between 250 and 350℃. Major efforts are underway in the industry to raise the maximum use temperature above 400℃. Compare this with neodymium-iron-boron's (NdFeB) maximum use temperatures of 150 to 200℃. Other advantages of SmCo over NdFeB include better corrosion resistance and greater magnetic output at temperatures above about 150℃.

Sensor applications requiring a stable magnetic field benefit from SmCo's low reversible temperature coefficient of induction: -0.030%/℃ 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 lower magnetic output.

Compression Bonded - this is a technique whereby a special form of SmCo powder is blended with a plastic carrier material, die pressed and then heated. Parts made in this way can be of complex shapes and come off the tool with close tolerances, requiring no further finish machining. They have lower energy products than sintered materials - currently in the range of 15 MGOe.