Samarium Cobalt Magnets
Samarium cobalt (SmCo) magnets are strong permanent magnets made of samarium, cobalt, and other minor elements. It is known for its high magnetic strength and good temperature stability. Samarium cobalt magnets are generally weaker than neodymium magnets at room temperature, but they perform reliably in extreme temperatures when neodymium magnets stop working. Since SmCo is highly resistant to corrosion and oxidation, coatings are generally not required. Since the samarium cobalt magnet is made by sintering, it is very brittle and cracks may appear inside.
SmCo5 alloy contains one samarium atom for every five cobalt atoms, and is the first generation of samarium cobalt magnets. The (BH)max of 1:5 SmCo alloys is from 15 MGOe to 25 MGOe and the service temperature is up to 250°C. SmCo5 mainly contains Sm and Co and does not contain iron, so it has better resistance to corrosion and demagnetization.
Compared with Sm1Co5, the magnetic properties of 2:17 SmCo alloy are better. Its (BH)max usually varies between 24 MGOe and 32 MGOe, and its working temperature can reach 300 °C. Sm2Co17 contains very few other elements such as iron, copper, and samarium and cobalt. The withdrawal of iron from this alloy means that it may corrode slightly in high humidity environments, so Sm2Co17 magnets are coated with nickel in some cases.