Elementary excitations and nonlinear dynamics of a magnetic domain wall

Two-dimensional magnons localized in the polarized 180^∘{} Bloch domain wall and its nonlinear dynamics at high ac drive field in an yttrium iron garnet single-crystal plate are investigated. The interaction between translational and flexural modes of the wall vibration is studied in detail. The excitation spectrum of the moving wall is shown to depend on its velocity. An unexpected asymmetric dependence of flexural mode eigenfrequencies and resonance linewidths on the wall velocity is found. The flexural waves themselves are found to influence the amplitude of the translational wall vibrations. Two kinds of instability were found at increasing drive field. The first is the transition from the periodic linear vibrations at low field and low wall mobility to weakly nonharmonic oscillations at high mobility. They are shown to be due to the excitation of the standing flexural modes of the wall. And the second one is the transition to the region of chaotic wall motion and low mobility at the highest field studied. The real-time signals, spectral data, and phase-space patterns corresponding to different regions were obtained. The phase portrait at the highest field studied is found to be of the chaotic attractor type.