Thermal remagnetization of Co5Sm magnets

Co5Sm magnets that are partly or fully demagnetized at room temperature regain some of their magnetization on heating. This phenomenon of thermal remagnetization, which is of importance in several applications, has been characterized as a function of prior treatment, magnet shape, temperature, and thermal cycling. A demagnetization-remagnetization pretreatment is found to provide stabilization against the effect. Domain studies by the Kerr effect demonstrate that thermal remagnetization in Co5Sm results from reduction of microscopic magnetostatic energy by domain rearrangement. Because of different domain behavior, precipitation-hardened cobalt-rare earth magnets exhibit little or no thermal remagnetization.