The reversible temperature coefficient of Permanent Magnets
 
 

It is apparent that, While the characteristic shape of demagnetization curves of permanent magnets retained as the magnet's temperature varies, the curve's position relative to each axis changes. In terms of a magnet's intrinsic demagnetization curve , its magnetization + Msat and its intrinsic coercivity - Hci are both changing with temperature. Because Br =¦Ì o Msat , the magnet's "normal" B vs. H curve will move by virtue of both its remanence Br and its coercivity -Hc changing with temperature.

 
 

Whatever flux density we expected the magnet to provide at room temperature, this will be different at any other temperature, directly affecting the performance of the motor in which the magnet is installed. Furthermore, the "knee" in the demagnetization curves represents the onset of a reversal of the material's magnetization , but now we see that the position of the "knee", and hence the threshold for magnetization reversal, is dependent upon temperature.