Samarium Cobalt Magnet

Samarium cobalt magnets are made from two metallic elements, samarium and cobalt, and are part of the family of magnets known as ‘rare earth’ magnets. When they were first developed in the 1970s, samarium cobalt magnets were revolutionary as the first commercially available rare earth magnet, but they were soon overtaken as favourite by neodymium magnets, which were a cheaper alternative. Both samarium cobalt magnets and neodymium magnets are of similar strength, but samarium cobalt magnets come into their own in extreme temperature environments. Heating magnets causes them to lose their magnetisation, as does making them very cold. But samarium cobalt magnets can operate in temperatures as low as absolute zero (-273°C) and keep their magnetisation up to 350°C, compared to a regular neodymium magnet’s comfortable temperature range of -130°C to 80°C.

This capability sees samarium cobalt magnets used in harsh operating environments, such as generators and motors. Since they don’t contain any iron, these magnets are also strongly corrosion resistant, making them handy in marine and offshore environments where they are exposed to corrosive saltwater. Their only drawback is that they are rather brittle and prone to cracking and chipping.

In the production of these magnets, a samarium cobalt powder is compacted in a rigid steel mould, pressed, and a magnetic field applied to align the particles. It is then sintered (heat and pressure is applied) to cause the powder to coalesce into a solid mass.