Regensburg 1998 – wissenschaftliches Programm

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AM: Magnetismus

AM 12: Mikromagnetismus, Magnetisierungsprozesse und Domänenstrukturen I

AM 12.6: Vortrag

Mittwoch, 25. März 1998, 16:15–16:30, H23

Calculation of the energy barriers in strongly interacting many-particle systems — •D.V. Berkov — INNOVENT e.V., Goeschwitzer Str. 22, D-07745 Jena, Germany

We present a new numerical method for the evaluation of the energy barriers between various local energy minima in strongly interacting classical many-particle systems with continuous degrees of freedom (’usual’ particles, vector spin glasses, dipolar glasses, systems of fine magnetic particles etc.). The method is based on the minimization of the action derived from the Onsager-Machlup functional [1] for the transition probability between the two given local minima. The corresponding minimization provides a discrete representation of the optimal transition trajectory between the two chosen states. The energy barrier between these states is then evaluated as the barrier along this optimal trajectory.
Special care should be taken to extract the ’true’ optimal trajectories (i.e., trajectories which pass through the saddle points) from a large variety of paths providing the local extrema to the action functional. Special algorithm designed for this purpose is described and tested on several model systems. Implementations of the algorithm for (i) the evaluation of the energy barrier distribution and (ii) the simulation of the time dependence of the system magnetization in disordered many-particle systems are suggested. Results for the dipolar magnetic glass are presented.

[1] L.Onsager, S.Machlup, Phys. Rev., 91, 1505 (1953)