SmCo

SmCo, or samarium–cobalt magnets, are a class of permanent magnets composed primarily of samarium and cobalt, with small additions of copper and zirconium in many grades. They were among the first commercially produced rare-earth magnets and are manufactured mainly by powder metallurgy. SmCo magnets are noted for high resistance to demagnetization and excellent thermal stability, making them suitable for demanding environments.

There are two major families: SmCo5 and Sm2Co17. SmCo5 magnets have a simpler Sm:Co ratio and good corrosion resistance, while Sm2Co17 magnets offer higher overall magnetic energy and better high-temperature performance. Both rely on strong magnetocrystalline anisotropy to achieve high coercivity.

Typical properties include a high energy product and high Curie temperatures, with operation in elevated temperatures up to roughly 250–350°C depending on grade. They also exhibit strong resistance to oxidation when properly coated, and have good resistance to demagnetization in challenging magnetic environments. However, they are relatively brittle and can be expensive.

Manufacturing commonly uses powder metallurgy with directional orientation to achieve magnetization along easy axes. Sintered SmCo magnets provide high performance and temperature stability; bonded forms exist but with lower magnetic strength. Applications include aerospace and defense components, high-temperature motors, actuators, sensors, and medical devices where temperature stability is critical.

SmCo magnets are more expensive and less widely used than neodymium-iron-boron magnets, but remain favored for extreme-temperature or corrosive environments. Their supply is tied to rare-earth and cobalt markets, which can affect cost and availability. Coatings such as nickel or nickel–phosphate are used to improve corrosion resistance.