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MA: Fachverband Magnetismus

MA 31: Magnetization Dynamics III

MA 31.3: Talk

Wednesday, March 16, 2011, 11:30–11:45, HSZ 403

Nonlinear magnon scattering in nano-sized Permalloy elements — •Henning Ulrichs¹, Vladislav E. Demidov¹, Sergej O. Demokritov¹, and Sergei Urazhdin² — ¹Institut für angewandte Physik, Universität Münster, Correnstraße 2-4, 48149 Münster, Germany — ²Department of Physics, West Virginia University, Morgantown, WV 26506, USA

In this talk we will report about nonlinear magnetization dynamics in sub-micron-sized elliptical Permalloy dots. The dynamics was excited using intense microwave pulses and studied by means of micro-focus Brillouin light scattering spectroscopy. In the linear regime, one predominantly observes excitation of the fundamental eigenmode of the dot, which resembles the FMR mode in such a confined geometry. At higher pulse powers a secondary, low-frequency mode is excited in addition to the fundamental mode. This process nucleates at the center of the dot, where the amplitude of the fundamental mode shows a maximum. Our explanation assumes a scattering of magnons of the fundamental mode into the lowest frequency state. This process is reminiscent of the initial phase in the formation of magnon Bose-Einstein condensate observed in low-loss garnet films.