Effect of Low Temperature on Neodymium Magnets

In addition to the magnetization state, permeance change and external magnetic field, permanent magnetic properties of Neodymium magnets will also be influenced by other external conditions, such as ambient temperature, mechanical shock and irradiation. Among all these factors, the impact of change in ambient temperature is particularly common and seriously. Permanent magnetic properties of Neodymium magnet generally deteriorate as the ambient temperature rises, and it came the concept of flux loss and Max. Operating Temperature. In fact, some customers are curious about the effect of low temperature on Neodymium magnets.

Relevant measurement data indicated that remanence and Max. Energy Products increases with decreasing temperature at first, then drop sharply below 135K. Many studies showed that Nd₂Fe₁₄B will have a spin reorientation transition at 135K. The easy axis of Nd₂Fe₁₄B gradually turned into 30 degree easy cone from c-axis.

Zhong Ke San Huan has researched the effect of temperature on Pr_2.79Nd_8.68Tb_1.90Dy_0.28(Cu, Al, Ga)_0.58Co_1.50Fe_78.51B_5.76. The remanence and Max. Energy Products decreases with decreasing temperature when below spin reorientation temperature 100k. By comparison, Pr₂Fe₁₄B can always keep easy axis on c-axis under low temperature and high temperature. Hence provided much better low-temperature hard magnetic properties to Pr-Fe-B magnets compared with Nd-Fe-B magnets. Pr-Fe-B magnets can serve the higher air gap magnetic field in extremely low temperature applications, therefore, propellant sensor for rocket and low-temperature free electron laser is all employed Pr-Fe-B magnets.

According to Permanent Magnets and Their Application by Parkers and Studders, ferrite magnets can’t be used below 214K due to its low-temperature flux loss. They also reported 198K is the reasonable lower limit for Alnico magnets. For Samarium Cobalt magnet, its intrinsic coercivity significantly rises with decreasing temperature, and remanence increases modestly. Lots of research shows that Samarium Cobalt magnets can be successful use as low as 2k which near to absolute zero.