Field dependence of the flexural domain wall modes

Abstract

The domain wall oscillations have been investigated in the frequency range 10–150 MHz by using a magneto-optical spectrometer for the case of parallel stripe domains in the thin films of substituted YIG. The equations of motion are modified in a perturbation approach to include in-plane field and stray fields arising from the magnetic charges on the film surfaces. The inclusion of the stray fields makes the wall structure Bloch-like in the center and Néel-like close to the surface of the film. Under uniform excitation, the walls can flex and give rise to infinitely many resonance frequencies. The resonance frequencies and the wall profiles for different flexural modes are calculated by considering a small amplitude wall displacement about the equilibrium wall position. It is shown that the even modes are symmetric and odd modes are antisymmetric about the center of the film. Experimentally, three modes ν0, ν1, and ν2 have been observed as a function of the applied in-plane field. The field dependence of the ν0 is seen to be in very good agreement with the theory. For higher modes, a good qualitative agreement is observed. Unlike the rigid wall model, the present theory explains the finite values of the resonance frequencies for all values of an applied in-plane magnetic field up to the saturation fields.