Transient and steady-state domain-wall velocities in a garnet film

The transient and steady-state domain-wall velocities are measured by a refined collapse method in a bubble garnet film. The usual average velocity as a function of pulse width shows very large velocity for short pulse width and relaxation to the steady state. The instantaneous velocity defined simply from the increments of wall displacement distance and pulse width shows that the velocity is nearly steady over about 10 ns. The steady-state velocity below the drive field of 500 Oe includes both a velocity component independent of drive field and a component increasing linearly with field. The former mode is not operative above 900 Oe. These are discussed from the theoretical predictions, together with the wall velocity in hard bubbles.