The dynamical behavior of magnetic domain walls and magnetic bubbles in single-, double-, and triple-layer garnet films

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Abstract
The dynamical behavior of straight magnetic domain walls and propagating magnetic bubbles in single‐, double‐, and triple‐layer lanthanum gallium garnet films is reported. In the study of straight walls in the single‐layer films, a good agreement is obtained between the observed and the calculated values of the domain‐wall width parameter Δ, the derivative of the peak velocity to in‐plane field at high in‐plane fields, and the derivative of the saturation velocity to in‐plane field at a moderate drive field and high in‐plane fields H1. The saturation velocity (at H1=0) decreases with decreasing film thickness, which is in disagreement with theoretical predictions. A propagating bubble in a single‐layer film exhibits an overshoot. In double‐ and triple‐layer films, the observed and calculated Δ values disagree in most cases, and the straight wall and propagating bubble saturation velocities are significantly higher than in single‐layer films. Overshoots and low‐frequency oscillations are observed in the saturation regime of straight walls. The resulting high wall masses are attributed to stacking of horizontal Bloch lines on the film surface(s). From the measurements in in‐plane fields, we conclude that the saturation velocity and the peak velocity in a double‐ and a triple‐layer film depend on the polarity of the in‐plane field, which is always perpendicular to the straight wall. It is found that the saturation region in double‐ and triple‐layer films can be subdivided in three parts. This is explained qualitatively, and a calculation is made of the saturation velocity in double‐ and triple‐layer films. This calculation shows good agreement with experimental results.