Berlin 2012 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 34: Magnetization / Demagnetization Dynamics III

MA 34.13: Vortrag

Mittwoch, 28. März 2012, 18:15–18:30, H 1012

Quantum mechanical contribution to the magnon dispersion in the Heisenberg model — •Julian Hüser and Tilmann Kuhn — Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster

The main contributions to the magnon dispersion in thin magnetic films are provided by the exchange and dipole-dipole interactions. Most fundamental work is based on the Heisenberg model which is able to explain this complex dispersion relation. It has been shown by several authors that by making the transition to classical spins a dispersion relation is obtained which is equal to the result of the harmonic spinwave approximation by applying either the Holstein-Primakoff or the Dyson-Maleev transformation. Because of the nonlinearity of these boson mappings higher-order terms which are omitted in the harmonic spinwave approximation react on the linear terms and thus modify the dispersion relation. Therefore, this modification is a purely quantum mechanical effect. However, this correction has mostly been neglected so far and barely investigations were made to confirm the validity of the harmonic spinwave approximation. The present work provides an analysis of this quantum mechanical effect and shows in which cases it is negligible or not.