Regensburg 1998 – wissenschaftliches Programm

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AM: Magnetismus

AM 12: Mikromagnetismus, Magnetisierungsprozesse und Domänenstrukturen I

AM 12.1: Hauptvortrag

Mittwoch, 25. März 1998, 14:30–15:15, H23

Thermally activated Magnetisation Reversal – a New Challenge for Micromagnets — •R. W. Chantrell — SEECS, University of Wales, Bangor, Gwynedd LL57 1UT, Great Britain

Standard (micromagnetic) theories of magnetisation processes essentially use variational techniques to determine minimum energy configurations. Magnetisation reversal occurs when a local minimum becomes unstable. Physically however, magnetisation reversal takes place by thermal activation over finite energy barriers whose determination is not possible within the usual micromagnetic framework. We will present a formalism for the simulation of thermally activated reversal processes based on the Langevin equation of the problem. The results demonstrate the importance of long wavelength correlated magnetisation fluctuations (spin waves) excited by the thermal perturbations. The paper will discuss some recent predictions of short timescale (ns) magnetisation reversal and highly structured (multilayered) magnetic materials which demonstrate complex dynamic behaviour and highlight the important effects of the physical microstructure on the magnetic behaviour.