Samarium Cobalt (Temperature Compensated)

About Samarium Cobalt Temperature Compensated Magnets

Temperature Compensated Samarium Cobalt magnets (first developed by EEC) provide a constant magnetic field strength over a temperature range of interest by customers.  For some applications such as traveling wave tubes (TWTs), gyroscopes and accelerometers, the reversible temperature coefficient of Br is required to be as low as possible. To address this requirement, we developed a series of temperature compensated Sm-Co magnets.

Key features of sintered SmCo magnets include:

  • Constant magnetic field strength across a temperature range of interest
  • Resistance to corrosion: highest for rare earth magnet materials
  • Highest resistance to demagnetization

 

 

 

Samarium Cobalt Temperature Compensated Magnetic Properties

Additional Information

Some magnet applications benefit from having a constant magnetic field strength over a temperature range of interest, or a small reversible temperature coefficient of residual induction (Br), α,  which  is defined as follows:

α = (ΔBr/Br) x (1/Δ T) × 100%

where ΔBr is the change of residual induction Br while ΔT is the change of temperature. For some applications such as traveling wave tubes (TWTs), gyroscopes and accelerometers, the reversible temperature coefficient of Br is required to be as low as possible. To address this requirement, we developed a series of temperature compensated SmCo magnets. Heavy rare earth (HRE) elements, such as Ho, Er, Gd, and Tb, can be substituted for a portion of the Sm in order to improve reversible temperature coefficient of residual induction. The following figure shows that, for Sm2TM17 (TM = transition metal) magnets, the residual induction, Br, decreases as temperature increases. As shown, Sm2TM17 magnets have a negative reversible temperature coefficient of residual induction. Conversely, the HRE2TM17 alloys have a positive reversible temperature coefficient of Br. By carefully adjusting the compositions, substituting HRE elements for a portion of the Sm, EEC has developed a series of temperature compensated SmCo 2:17 magnets with reversible temperature coefficient of Br very close to zero, as shown by the (Sm,HRE)2TM17 data points. [caption id="attachment_191" align="aligncenter" width="283"]SmCoTempCompEquation Temperature dependence of residual induction Br for Sm2TM17, (Sm,HRE)2TM17 and HRE2TM17 magnets (TM=transition metals, HRE=heavy rare earth)[/caption] The typical reversible temperature coefficient (RTC) of Br is calculated between -50 and 150°C. The fully compensated EEC2:17TC-16 magnets have a typical RTC of -0.001%/°C. EEC works closely with customers to establish correlation between the measurement of RTC of Br and performance in the actual device over the temperature range of interest. Typical applications which benefit from using temperature compensated SmCo magnets include gyroscopes, accelerometers, traveling wave tubes (TWTs) and high precision weighing scales. Please contact EEC engineering department if the RTC of Br is critical for your application. We can work with you to determine the best possible composition for your specific application.

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