Berlin 2015 – scientific programme

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MA: Fachverband Magnetismus

MA 27: Magnetization / Demagnetization Dynamics I

MA 27.12: Talk

Wednesday, March 18, 2015, 12:30–12:45, EB 301

Ferromagnetic relaxation in yttrium iron garnet at small wave vectors — •Julian Hüser and Tilmann Kuhn — Institut für Festkörpertheorie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster

Shortly after the discovery of yttrium iron garnet (YIG) in 1956, a lot of investigations have been performed on this unique magnetic material which to the present has the smallest known ferromagnetic resonance line width. Thereby, a problem occured in explaining the very fast thermalization of pumped magnons in recent experiments in the field of Bose-Einstein condensation of magnons. This fast thermalization is typically interpreted as a multi-stage four-magnon scattering process. However, according to the standard derivation, the contribution of the four-magnon scattering to the relaxation of low energy magnons vanishes in the limit of zero wave vector and therefore this process is far too weak in order to account for thermalization at very small wave vectors where the minimal energy state is located.

In this work, we study the intrinsic relaxation mechanisms and present an additional contribution which has been neglected so far. We show that this contribution is strong enough to explain the experimentally observed fast magnon thermalization.