Eigenmode images (top) and spatially averaged power spectra (middle) for a ellipse of Permalloy in zero applied field. The spectra and images were obtained from three time series following excitation field pulses with three different symmetries. The calculated mode frequencies (center) are compared with frequencies calculated from a spinwave dispersion relation (bottom). The end mode frequency is labeled “” and the uniform precession frequency for an ellipse is labeled “.”
Normal modes and spectral density for a thick, diam cobalt disk for (a) modes with even symmetry and (b) modes with odd symmetry. Because the second odd mode is nonuniform both in plane and normal it is most likely to be driven unstable by a spin current.
Applied field dependence of normal mode frequencies. Crosses are for even -symmetry modes and circles are for odd -symmetry modes. The line shows the extrapolation of the second odd mode to zero field.
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