Samarium cobalt (SmCo) magnet is a type of strong permanent magnet made of samarium, cobalt and few other elements. It is known for its high magnetic strength and good temperature stability. SmCo magnet is usually weaker than Neodymium magnet at room temperature, however, it still performs reliable in extreme temperature when Neodymium magnet is out of work. SmCo is usually unnecessary to be coated for its strong resistance to corrosion and oxidation. Since the samarium cobalt magnet is made by sintering, it is very brittle and may have cracks inside.
The SmCo5 alloy contains one atom of samarium per five atoms of cobalt, it is the first generation of SmCo magnet. The 1:5 SmCo alloy offers (BH)max from 15 MGOe to 25 MGOe and its working temperature is up to 250℃. SmCo5 contains mainly Sm and Co without Iron so it has better resistance to corrosion and demagnetization.
Compared with SmCo5, the 2:17 SmCo alloy performs better in magnetic properties. Its (BH)max usually vary from 24 MGOe to 32 MGOe and its working temperature is up to 300℃. The Sm2Co17 contains few other elements like iron, copper as well as samarium and cobalt. The exit of iron in this alloy means it may occur slight corrosion in high humidity environments, so Sm2Co17 magnets are coated with nickel in some cases.