A Brief Introduction to Temperature Compensated SmCo Magnets

High performance SmCo magnets, ultra-high temperature SmCo magnets, and temperature compensated SmCo magnets are three research hotspots in Samarium Cobalt SmCo magnets area. Temperature coefficient of remanence α_Br of conventional SmCo magnets are already quite low in comparison with other commercially available permanent magnetic material, especially Neodymium magnets and ferrite magnets. But it still cannot satisfy the extremely low α_Br applications in aerospace and precision instruments, such as travelling wave tubes, gyroscopes, and accelerometers. Therefore, low α_Br SmCo magnets, which also known as temperature compensated SmCo magnets, were developed to address those high temperature stability applications. The α_Br of temperature compensated SmCo magnets is very close to zero and thus providing constant magnetic field strength across a certain range of temperature. Besides low α_Br SmCo magnets, SDM has also mastered mass production of zero temperature coefficient magnets and positive temperature coefficient magnets.

For rare earth-transition metal (RE-TM) alloy, magnetization decreased with increasing temperature when RE is light rare earth elements (LREEs, LREEs= Sm, Nd, Pr, Ce). However, magnetization of alloy present non-linear change trends with temperature when RE is heavy rare earth elements (HREEs, HREEs= Gd, Tb, Er, Ho). Take RETM₅ alloy as an example, saturation magnetization of GdCo₅ and ErCo₅ increased with the increasing temperature in the range of -150~450 and -270~250 degrees Celsius, respectively. This is mainly because ferrimagnetic coupling characteristic which produced by antiparallel arrangement of HREEs and Cobalt’s atomic magnetic moment. Therefore, replace Samarium by moderate Gadolinium or Erbium will be able to manufacture low α_Br (Sm, HREEs)Co₅ magnets due to decline of saturation magnetization in SmCo₅ is compensated by HREEsCo₅. 2:17 type Sm₂(Co, Cu, Fe, Zr)₁₇ magnets can also manufacture temperature compensated magnets by substituting middle rare earth elements (MREEs) and HREEs for Samarium which completely similar like 1:5 type SmCo magnets.