Determining the maximum operating temperature of permanent magnets via in-situ measurement of the magnetic flux

The temperature stability of a magnet is crucial for applications. Traditionally, the designers determine the maximum operating temperature (T-o(m)) of a permanent magnet by either the linearity of the B(H) curve or the irreversible flux loss. However, the reliability and efficiency of the traditional methods are challenging. Here, a new method of "in-situ measurement of the magnetic flux at elevated temperature" is introduced. By studying the temperature-dependence of magnetic flux for the Nd-Fe-B magnet, we find that the magnetic flux declines linearly as the temperature increases. Upon approaching a specific temperature, there occurs a rapid and nonlinear decline of magnetic flux.This temperature can be defined as T-o(m). Furthermore, the magnetic flux dependence on time at elevated temperature is also investigated, wherein the logarithmic relaxation is observed. The decay rate of magnetic flux could be related to the exposure temperature. If the decay rate of maximum magnetic flux loss is acceptable below a given temperature, we can also define the temperature as T-o(m).