Gradient propagation, overshoot, and creep in magnetic-bubble garnet material

Gradient propagation of free magnetic bubbles has been investigated using high-speed transient photography. Overshoot in the translational motion was confirmed and a new mode of motion, creep, was introduced. Creep is induced translational motion caused by bias-field pulsing after a driven translation and overshoot. It was found that overshoot is bubble-size (bias-field) dependent and that creep and overshoot are complementary with the total motion independent of the bias field. A model is presented that provides that the wall structure at the end of the gradient pulse be dominated by these vertical wall twists, i.e., vertical Bloch line pairs with each having a winding direction opposite the other. This structure is packed by the g forces during translation and relaxes after the termination of the pulse to give overshoot. Creep is the result of annihilating the remaining wall twists by bias-field pulsing as the wall assumes its most stable state.