Samarium Cobalt (SmCo) magnets are made by a sintering process and exist in two forms. The first is Sm1Co5 (SmCo 1:5) and this has a maximum energy product of between 14 and 24 MGOe. The second, and more common, form is Sm2Co17 (SmCo 2:17) and this has a maximum energy product of between 22 and 32 MGOe. The main Sm2Co17 alloy is around 35% Samarium (Sm) and 60% Cobalt (Co), with the balance from varying amounts of Iron (Fe), Copper (Cu), Hafnium (Hf) and Zirconium (Zr). Praseodymium (Pr) may also be used. Sm1Co5 is made of only Sm and Co and has excellent corrosion resistance.

Samarium Cobalt (SmCo) magnets can be used over a wide temperature range. SmCo can be used down to a few Kelvin above Absolute Zero, making them a first choice magnet for cryogenic applications. They can also be used in very high temperatures, up to 350 °C, depending on the grade.

Samarium Cobalt (SmCo) magnets contain less free iron than Neodymium magnets and therefore provide better corrosion resistance than Neodymium magnets. It is very rare for SmCo magnets to require protective plating. This characteristic, together with good demagnetization resistance, make Samarium Cobalt magnets suitable for use in extreme working conditions.