Berlin 2005 – scientific programme

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MA: Magnetismus

MA 18: Magnetische dünne Schichten III

MA 18.7: Talk

Monday, March 7, 2005, 12:00–12:15, TU H1028

Hysteresis mediated by a domain wall motion — •Thomas Nattermann¹ and Valery Pokrovsky² — ¹Institut für Theoretische Physik der Universität zu Köln, Zülpicher Str. 77, 50937 Köln — ²Department of Physics, Texas A&M University, College Station TX, USA

The position of an interface (domain wall) in a medium with random pinning defects is not determined unambiguously by the instantaneous value of the driving force, even on average. Employing the general theory of the interface motion in a random medium, we study this hysteresis, different possible shapes of the hysteresis loop, and the dynamical phase transitions between them. Several principal characteristics of the hysteresis, including the coercive force and the curves of dynamical phase transitions obey scaling laws and display a critical behavior in the vicinity of the mobility threshold. At finite temperature the threshold is smeared and a new range of thermally activated hysteresis appears. At a finite frequency of the driving force there exists a range of the non-adiabatic regime in which not only the position, but also the average velocity of the domain wall, displays hysteresis.