Domain wall dynamics in CoFeSiB microwires under axial applied stress

In this work, we present a domain wall dynamics study on Joule heated Co68.15Fe4.35Si12.5B15 glass-covered amorphous microwires. Three samples were annealed with: (i) DC current or AC current with frequency of (ii) 100 Hz and (iii) 500 Hz. The current density was equivalent to an annealing temperature of 250 deg. C . The permeability spectra were obtained from the magnetoimpedance measurements at different axial applied stresses. Contributions from domain wall motion and magnetization rotation to the total permeability were separated and analyzed. Without axial stress, the samples present a longitudinal anisotropy, which is converted to a core-shell domain structure (bamboo-like structure) when stress is applied. A huge increase of domain wall component of the permeability until a critical stress followed by a linear reduction is present in all samples. The main difference is that the domain wall contribution to the permeability and the critical stress are lowest for the DC annealed sample and reach a maximum for the sample annealed at 500 Hz. The results are discussed in terms of the field-induced anisotropy during the annealing and the internal stress distribution