Micron sized ferromagnetic permalloy disks exhibiting an in-plane ferromagnetic vortex structure are excited by a perpendicular magnetic field pulse and their modal structure is analyzed. Two types of modes are observed: radially symmetric modes with circular nodes and symmetry breaking modes with diametric nodes. The frequency of the modes with circular nodes increases with the number of nodes. In contrast, the frequency of the modes with diametric nodes decreases with the number of nodes. By a fourier filtering technique the time dependence of individual modes are separated and analyzed. These measurements are the first clear demonstration that mode-mode coupling plays a significant role in magnetization dynamics.
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