SamariumKobalt

Samarium cobalt magnets are a class of permanent magnets composed of intermetallic compounds of samarium and cobalt. The two principal compositions are SmCo5 and Sm2Co17, produced mainly as sintered magnets and, less commonly, as bonded magnets. They are known for high magnetic anisotropy and strong resistance to demagnetization.

Manufacture and composition typically rely on powder metallurgy, followed by controlled heat treatment to develop a hard, magnetically aligned microstructure. Small additions of elements such as iron, copper, and zirconium help optimize performance and grain boundary characteristics. Sintered SmCo magnets generally offer the best combination of strength and temperature stability, while bonded variants provide greater flexibility in shaping.

Key properties include a high energy product, usually in the range of 10 to 25 MGOe depending on grade, excellent thermal stability with operation at elevated temperatures, and strong resistance to demagnetization. They also exhibit high Curie temperatures. However, SmCo magnets are brittle and relatively expensive, and they typically require protective coatings (for example nickel or zinc) to guard against corrosion.

Applications are concentrated in environments where high-temperature or corrosive conditions prevail, such as aerospace, defense, automotive actuators, sensors, and specialized motors. While NdFeB magnets offer higher maximum energy products, SmCo magnets retain superior high-temperature performance and corrosion resistance, which makes them indispensable for certain extreme applications.

The development of samarium cobalt magnets dates to the 1960s, with significant contributions from Japanese and other international research and industry teams. They remain in use today in niche applications where their distinctive thermal and chemical stability is essential.