The magnetization behaviors show a strong pinning effect on domain wall motion in optimally melt-spun Pr8Fe87B5 ribbons at room temperature. According to analysis, the coercivity is determined by the nucleation field of reversed domain, and the pinning effect, which results from the weak exchange coupling at interface, makes domain nucleation processes independent and leads to non-uniform magnetization reversals. At a temperature of 60 K, owing to the weak exchange coupling between soft-hard grains, magnetization reversal undergoes processes of spring domain nucleation in soft grains and irreversible domain nucleation in hard grains, and the pinning effect remains strong among hard grains.

The irreversible magnetization is investigated by thermal activation, which results from the nucleation of reversed domain from defect region at grain surface to perfect region within grain owing to the self-interaction. In the irreversible magnetization, the self-interaction unit involves two parts, i.e., the domain wall in perfect region and a small part in defect region. A larger volume of defect region involved in the self-interaction unit leads to the significant reduction of energy barrier, resulting in a lower coercivity. These investigations demonstrate that magnetization behavior could be manipulated by the self-interaction at grain outer layer.