Static and dynamic behavior of domain walls in high B _S soft magnetic ribbons tuned by the annealing temperature

In this paper, we study the domain wall dynamics in high magnetic flux density (BS - 1.82 1.85 T) of soft magnetic ribbons Fe_81.2Co₄Si_0.5B_9.5P₄Cu_0.8 prepared with various annealing conditions. It is observed that annealing these ribbons beyond a temperature (Ta ∼ 400 °C) crystalizes the alloy with the appearance of α-Fe(-Co) phase. The post annealing leads to a change from amorphous to nanocrystalline phase accompanied by a reduction in internal stress in the ribbons. Domain imaging has been performed under both dc and ac fields to study the domain wall behavior in these ribbons. A wide variety of domain structures are observed in ribbons prepared with different annealing temperature as a result of the change in the intrinsic anisotropy. Under an ac magnetic field, the stress patterns in the amorphous ribbons are robust. However, ribbons with reduced stress (i.e. nanocrystalline) exhibit domain wall propagation which hints at a significant reduction in magnetocrystalline and magnetoelastic anisotropies due to uniform nanocrystallization. The ribbon annealed at Ta ∼ 460 °C exhibits static domain patterns resulting from strong pinning centers created by Fe-B precipitates.