Eddy-current anomaly in Fe-based nanocrystalline wires

The circular permeability, μ=μ′−jμ″, of two Fe-based nanocrystalline wires obtained by furnace annealing (S1) and by current annealing (S2) were determined from the measurements of the impedance, Z=R+jωL, as a function of frequency (f=0.1-100 kHz) and DC bias field (H=0-89 kA/m). So the H-dependent low-f eddy-current anomaly factor, η(H), has been investigated. The experimental results indicate that the sample S2 by current annealing has a larger η=4 than the sample S1 by furnace annealing with η=2.8 at H=0. With increasing H, the η(H) of two samples decreases initially until about H=450 A/m, and then increases very quickly. These results have been analyzed by the helical magnetization model considering the contribution of domain wall displacements (DWD) and domain magnetization rotation (DMR).