These are anisotropic substances that produce the highest specific energy.
Samarium-Cobalt alloy has been well known since the 70s. There are two main variants:
- the Sm C05 compound, which has a higher coercitive field and is principally used for motors, actuators and demagnetisation fields;
- the Sm2 C017 compound, which has a higher flux and is particularly used for audio applications, sensors, etc.
This family is characterised by a good temperature resistance:
- 0.04 % / °C on Br, on average,
- reversible behaviour up to approximately 120°C, at least,
- utilisation is possible up to 260°C (350°C for certain varieties).
Bremag 18 is particularly hard and brittle. It must never be force-fitted.
Resistance to corrosion is considered to be moderate to good, depending on the environment.
This composition is much more stable than Neodyme-Iron-Boron. But with very high energy values, the presence of cobalt can make handling extremely delicate.