These samarium–cobalt magnet alloys (generally written as SmCo5, or SmCo Series 1:5) have one atom of rare earth samarium per five atoms of cobalt. By weight this magnet alloy will typically contain 36% samarium with the balance cobalt. The energy products of these samarium–cobalt alloys range from 16 MG·Oe to 25 MG·Oe, that is, approx. 128–200 kJ/m3. These samarium–cobalt magnets generally have a reversible temperature coefficient of -0.05%/°C. Saturation magnetization can be achieved with a moderate magnetizing field. This series of magnet is easier to calibrate to a specific magnetic field than the SmCo 2:17 series magnets.
Sintered Samarium Cobalt magnets exhibit magnetic anisotropy, meaning they can only be magnetized in the axis of their magnetic orientation. This is done by aligning the crystal structure of the material during the manufacturing process.
These alloys (written as Sm2Co17, or SmCo Series 2:17) are age-hardened with a composition of two atoms of rare-earth samarium per 13–17 atoms of transition metals (TM). The TM content is rich in cobalt, but contains other elements such as iron and copper. Other elements like zirconium, hafnium, and such may be added in small quantities to achieve better heat treatment response. By weight, the alloy will generally contain 25% of samarium. The maximum energy products of these alloys range from 20 to 32 MGOe, what is about 160-260 kJ/m3. These alloys have the best reversible temperature coefficient of all rare-earth alloys, typically being -0.03%/°C. The "second generation" materials can also be used at higher temperatures.
•Extremely resistant to demagnetization
•Good temperature stability (maximum use temperatures between 250 °C (523 K) and 550 °C (823 K); Curie temperatures from 700 °C (973 K) to 800 °C (1,070 K)
•Expensive and subject to price fluctuations (cobalt is market price sensitive)
Physical and mechanical properties
Comparison of physical properties of sintered neodymium and Sm-Co magnets
Samarium - cobalt magnet has a strong resistance to corrosion and oxidation resistance, usually do not need to be coated can be widely used in high temperature and poor working conditions