  We report on detailed broadband ferromagnetic resonance measurements of
azimuthal and radial spin wave excitations in circular Permalloy dots in the
vortex ground state. Dots with aspect ratio (Beta =height over radius) varied
from 0.03 to 0.1 were explored. We found that for Beta exceeding approximately
0.05, variation of the spin wave eigenfrequencies with Beta deviates from the
predicted dependence. The frequency splitting of two lowest azimuthal modes was
observed. The experimentally observed dependence of the frequency splitting on
beta was reasonably well described by dynamic splitting model accounting the
spin-waves and, vortex gyrotropic mode interaction.
