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MA: Magnetismus

MA 27: Spindynamik II

MA 27.13: Vortrag

Dienstag, 8. März 2005, 18:15–18:30, TU H1012

AC-driven Domain Walls in Random Media — •Andreas Glatz¹, Thomas Nattermann¹, and Valery Pokrovsky² — ¹Institut für theoretische Physik, Universität zu Köln, Zülpicher Str. 77, 50937 Köln — ²Department of Physics, Texas A&M University, College Station, Texas 77843-4242

The viscous motion of an interface driven non-adiabatically by an ac external field of frequency ω₀ in a random medium is considered. The velocity exhibits a smeared depinning transition showing a double hysteresis in the case when the amplitude of the external field is larger than the depinning field. This hysteresis is absent in the adiabatic case ω₀ → 0. Using scaling arguments and an approximate renormalization group calculation we explain the main characteristics of the hysteresis loop. In the low frequency limit these can be expressed in terms of the depinning threshold and the critical exponents of the adiabatic case. If the amplitude is smaller than the depinning field, also the avalanche motion of the interface has to be taken into account leading to a pronounced effect in the velocity hysteresis.