  The dynamics of micrometer-sized magnetic domains in ultra-thin ferromagnetic
films is so dramatically slowed down by quenched disorder that the spontaneous
elastic tension collapse becomes unobservable at ambient temperature. By
magneto-optical imaging we show that a weak zero-bias AC magnetic field can
assist such curvature-driven collapse, making the area of a bubble to reduce at
a measurable rate, in spite of the negligible effect that the same curvature
has on the average creep motion driven by a comparable DC field. An analytical
model explains this phenomenon quantitatively.
