According to their materials, rare earth magnets can be classified into two basic types: Neodymium Iron Boron rare earth magnets and Samarium Cobalt rare earth magnets.
Neodymium Iron Boron (NdFeB) – Energy products go up to 55 MGOe, can generate very high fields; however, typically needs to be used in lower temperature applications than Samarium Cobalt can withstand. Higher temperature coefficient of Br (approximately 1.1%).
Sintered neodymium-iron-boron (Nd-Fe-B) magnets are licensed rare earth magnets which are the most powerful commercialized permanent magnets available today, with maximum energy product ranging from 26 MGOe to 52 MGOe. Neodymium Iron Boron is the third generation of permanent magnet developed in the 1980s. It has a combination of very high remanence and coercivity and comes with a wide range of grades, sizes and shapes. With its excellent magnetic characteristics Nd-Fe-B offers flexibility for new designs or as a replacement for traditional magnet materials such as ceramic, Alnico and Sm-Co for achieving higher efficiency and more compact devices.
Samarium Cobalt (SmCo) – Energy products go up to 32 MGOe, can typically be used in high temperature (350°C) environments, and typically have a small thermal coefficient of Br (approximately 0.03%/degree).
Sm-Co materials come in energy products from 16 MGOe up to 33 MGOe. Their high resistance to demagnetizing influences and excellent thermal stability has ensured Sm-Co as the premium choice for the most demanding motor applications. In addition, the corrosion resistance is significantly higher than, for example, Nd-Fe-B. It is still recommended to coat the magnet in acidic conditions. Its corrosion resistance has also offered a high degree of comfort to those looking to use magnets in medical applications.