Domain wall kinetics in soft ferromagnetic metallic glasses

Domain wall kinetics are studied in glassy iron-base wire and iron-nickel–base ribbon. These materials exhibit high wall mobilities. The wire is examined in a single-wall regime below the nucleation field. Here reversal takes place by propagation of a domain wall of 2.5-cm axial length along the wire. The mobility normal to the wall is 270 cm/sec Oe. In the case of glassy iron-nickel–base ribbon the number of walls taking part in reversal is measured to be two. Using this number, the wall mobility is 1700 cm/sec Oe. The viscosity limiting the wall mobility is partitioned into a (calculated) eddy-current contribution and a spin-relaxation contribution. The latter constitutes about 40% of the total viscosity in the wire and about 50% in the ribbon samples. Gilbert damping constants for these samples, 0.44 (wire) and 0.19 (ribbon), are small compared with similarly obtained values for comparable polycrystalline alloys.