Magnetoimpedance aftereffect in a soft magnetic amorphous wire

A slow relaxation of the high-frequency impedance is observed in a ${\mathrm{Co}}_{68.25}$ ${\mathrm{Fe}}_{4.5}$ ${\mathrm{Si}}_{12.25}$ ${\mathrm{B}}_{15}$ amorphous wire after nucleation of a new domain pattern in a previously saturated sample. The observed impedance decay follows quasilogarithmic kinetics, and it is probably associated with the low-field ac magnetic permeability aftereffect of the circular domain walls. The impedance drop achieves relative amplitudes up to 1%, 16 s after the removal of the saturating external field. The effect is studied under typical magnetoimpedance experimental conditions, varying both the ac current amplitude and frequency. Although completely undesirable for many technical applications, the unique kinetic features of the impedance aftereffect may be explored to study circular magnetization processes under extreme domain-wall velocities.