Domain wall kinetics in soft ferromagnetic metallic glasses

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Abstract
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.