Static and dynamic behavior of domain walls in highB_Ssoft magnetic ribbons tuned by the annealing temperature

Abstract

In this paper, we study the domain wall dynamics in high magnetic flux density (–1.85 T) of soft magnetic ribbons Fe81.2Co4Si0.5B9.5P4Cu0.8 prepared with various annealing conditions. It is observed that annealing these ribbons beyond a temperature (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 C exhibits static domain patterns resulting from strong pinning centers created by Fe-B precipitates.

Tuning the anisotropy and domain structure of Co films by variable growth conditions and seed layers

“…On the other hand, films with extremely low anisotropy is often desired in transformers, microwave devices, etc [12,13]. The foundation for excellent soft-magnetic properties are provided by the suppressed magneto-crystalline anisotropy and low magnetostriction [14]. Presence of the induced UMA also may hinder other anisotropy contributions which are desired to tune the effective anisotropy of the system [15,16].…”

Nano-crystallisation and magnetic softening in Fe–B binary alloys induced by ultra-rapid heating

“…One of the most successful examples of utilizing the crystallisation of amorphous alloys in technological applications is the Fe-based nanocrystalline soft magnetic alloys [1] prepared from melt-spun amorphous precursors. The first example of alloy development in this class of soft magnetic materials was reported by Yoshizawa et al [2] in 1988, which was followed by the development of many new alloys prepared similarly by the nano-crystallisation of melt-spun amorphous precursors [3][4][5][6]. The effect of the magnetocrystalline anisotropy (K 1 ) in these alloys is exchange-averaged and magnetic softening occurs simply by nanoscale grain refinement.…”

“…Since the exchange-softening effect takes place where the grain size (D) is smaller than the natural exchange length ( L 0 ex = 30 − 40 nm in Fe-based alloys) [1], the nanostructural formation upon the crystallisation of amorphous precursors is a primary condition in the alloy development. To realize nano-crystallisation, the vast majority of alloys developed to date contain a considerable amount of additives such as Nb [2,3], Cu [2][3][4][5][6], and P [6]. Among these additives, the roles played by Cu and Nb were studied extensively; Cu is known to enhance heterogeneous nucleation [12] while Nb is believed to inhibit the crystal growth process [13] during nano-crystallisation in Fe-based alloys.…”