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Non-adiabatic AC-Dynamics of Disorderd Elastic Systems

Andreas Glatz **Argonne National Lab**
__Abstract:__

The viscous motion of an interface driven non-adiabatically by an ac

external field of frequency omega_0 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

omega_0 to 0.

Using scaling arguments and an approximate renormalization group calculation

we explain the main characteristics of the hysteresis loop [1]. In

the low frequency limit these can be expressed in terms of the depinning

threshold and the critical exponents of the adiabatic case.

We use these results to explain experimental measurements of the domain

wall motion in granular >superferromagnetic materials.

We calculate the complex susceptibilities

numerically, and compare the Cole-Cole representations [2].

[1] A. Glatz, T. Nattermann, and V. L. Pokrovsky, Phys. Rev. Lett. 90,

047201 (2003).

[2] O. Petracic et al., J. Mag. Magn. Mat. 272, E1201 (2004).