Observation of straight and wavelike domain wall motion in bubble films by high speed photography

The motion of domain walls in garnet bubble films has been studied by means of a high speed photographic technique with 10 nsec resolution. A straight, isolated stripe was stabilized in a DC bias field, and a strong reverse field pulse was applied. Initially the two walls remained straight as the stripe expanded. This wall motion proceeded with a saturation velocity which was generally higher than but within 50% of that determined from dynamic bubble collapse. After the stripe had widened to typically several times its initial size, a wavelike distortion with a characteristic wavelength developed on each side of the stripe. A simple magnetostatic model is shown to predict such a wavelike instability at the observed stripe width and wavelength.