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DF: Dielektrische Festkörper

DF 7: Dielectric and Ferroelectric Thin Films and Nanostructures II

DF 7.6: Vortrag

Mittwoch, 29. März 2006, 16:10–16:30, K{\"O}N Farb

Computational investigations on the Kohlrausch relaxation law for interacting dipole systems — •Markus Kühn and Herbert Kliem — Saarland University, Institute of Electrical Engineering Physics, P.O. Box 151150, 66041 Saarbrücken, Germany

For an interacting system of permanent dipoles calculations of transient polarization relaxations show a pronounced Kohlrausch behaviour. It can be described in the time domain by stretched exponential functions or power laws. The model which is employed here is based on permanent dipoles which fluctuate thermally activated in double-well potentials. The dipoles are statistically distributed with respect to their centres and the direction of their axes. The long-range electrostatic dipole-dipole interaction strongly influences the local fields at the dipoles. The iterative algorithm mainly consists of two steps. For each current configuration the local electric fields at the dipoles are deterministically calculated. Then the transition times of the dipoles which depend on the local electric fields are computed in a following weighted probabilistic Monte Carlo step. Simulation results yield a strong dependence of the Kohlrausch behaviour on the dipole charge, the dipole length and the dipole density. Further calculations show the influence of the geometrical dimensions, the temperature, the intrinsic activation energy for a dipole flip and the external electric field.