Domain-wall surface energy derived from the complex impedance of Metglas ribbons traversed by ac currents

An electric current I crossing plane domain walls causes a distortion which increases wall area, hence total wall energy. This stored energy ∝ I2 manifests itself as a contribution to the imaginary part of the complex impedance Z of a ribbon. We can obtain the wall surface energy σ per unit area from measurements of Z. We have measured Z in a 21 μm×361 μm×6.6 mm piece of nonmagnetostrictive Metglas 2705X between 200 Hz and 50 kHz. The sample has been mechanically polished and annealed in a magnetic field transverse to the length.