The temperature dependence of the coercive field of Co5Sm magnets

The temperature dependence of the coercive field Hsub(c) of Co5Sm has been investigated between 4.2 and 300 K. In magnets with high coercive fields a strong dependence of the magnitude of Hsub(c) on the heat treatment is found, whereas the temperature dependence of Hsub(c) remains unaffected. The coercive field is attributed to the expansion of small reversed domains and to the pinning of domain walls at planar defects. In low coercive materials and in well-annealed Co5Sm single crystals a considerably stronger temperature dependence of Hsub(c) is found which is quantitatively explained by pinning of two-dimensionally vaulted domain walls at randomly distributed defects. Below 100 K the Peierls potential of the narrow domain walls plays a significant role whereas its influence is smeared out at higher temperatures by thermally activated Bloch-wall diffusion. (Auth.)