Temperature dependence of coercivity of cellular Sm2Co17−SmCo5 permanent magnets

The spontaneous magnetization and the coercive field of sintered Sm(Co, Fe, Cu, Zr)7.6 alloys of cellular microstructure which were annealed at 775°C (sample A1) and also at 400°C (sample A2), were measured in the temperature range between 4.2and 1200 K. Materials A1 show an intrinsic type magnetic hardness with exponential type temperature dependence at cryogenic temperatures. Samples given subsequent heat treatments at lower temperatures (A2) show a more or less linear temperature dependence of the coercive field resulting in μ0HC = 7.6 T at 4.2 K. Implications of these findings for an understanding of the magnetic hardening process in cellular magnets are discussed.