Study of magnetization reversal and magnetic hardening in SmCo5 single crystal magnets

Large SmCo5 single-crystal spheres are used as simple model objects for both theoretical and practical studies of the coercivity mechanism in permanent magnets (PM). These samples exhibit coercivity values exceeding 1 T, achieved through the enhancement of surface smoothness. The morphology and magnetic results indicate that surface defects play a key role in the reversal mechanism and nucleation process. The reversal mechanism and coercivity are studied by means of different magnetization protocols, shedding light on the influence of two types of nucleus of reversal magnetic domains. We then utilize these objects to probe the angular dependence of coercivity. Our examination of samples with differing surface states reveals that enhanced surface smoothness corresponds to a behaviour closer to the coherent rotation model. This study underscores the massive influence of surface defects on magnetization reversal. Thus, the reduction of imperfections in PM grain boundaries holds the potential to significantly increase the nucleation field and thus the coercivity. More generally, our study introduces a methodology for examining the magnetization reversal of permanent magnets using simple model objects.