Samarium–cobalt magnet

Samarium-cobalt magnets (SmCo₅) are composed of samarium and cobalt. They have been available since the early 1970s. This sort of rare-earth magnet is very powerful, however they are also very brittle and prone to cracking and chipping. Although more expensive and not as powerful as neodymium magnets, samarium-cobalt magnets have a higher Curie temperature and can be used for higher-temperature applications.

This material poses a fire hazard if ground when dry, since the grinding dust has a low temperature ignition point.

Even small samarium-cobalt magnets can be hazardous, being able to pinch skin or fingers when suddenly attracted to another magnetic object. Large-sized samarium-cobalt magnets should be kept out of reach of small children. Any magnets should also be stored away from electrical appliances, magnetic (e.g. bank) cards and cathode ray tubes (e.g. some televisions and computer displays), as damage may be irreparable.

Attributes

• High resistance to demagnetization
• High energy (magnetic strength is strong for its size)
• Good temperature stability (maximum use temperatures between 250 and 350 °C; Curie temperatures from 700 to 800 °C)
• Expensive material (cobalt is market price sensitive)

Material properties

• Density: 8.4 g/cm³
• Electrical Resistivity 0.8×10⁻⁴ Ω·cm
• Coefficient of thermal expansion (perpendicular to axis): 12.5 µm/(m·K)