Developed in the early 1960s by Karl Strnat at Wright-Patterson Air Force Base and Alden Ray at the University of Dayton, SmCo5 was the first commercialized rare-earth permanent magnet.
Manufactured in hexagonal 1:5 (SmCo5, 16–25 MGOe) and rhombohedral 2:17 (Sm2(Co,Fe,Cu,Zr)17, 20–32 MGOe) series, it operates continuously at 250–550 °C with Curie temperatures of 700–850 °C.
With a reversible temperature coefficient of remanence as low as −0.03%/K and intrinsic oxidation resistance requiring no plating, SmCo is preferred in aerospace actuators, traveling-wave tubes, and inertial gyroscopes.