Experimental observation of Bloch curves in bubbles

The rotating gradient technique was used to study magnetic bubble domain wall spin structures that exist only in a moving wall and are not stable in a bubble at rest. Recently, true steady-state motion of a circularly propagating bubble has been observed and characterized by performing the rotating gradient experiment without the use of applied in-plane fields, making this the first experiment in which dynamically stable twist structures that are not distorted by in-plane fields canbe expected to be observed. The wall structure was probed by comparing the experimentally measured velocity-momentum relation for rotating bubbles with the predicted relations for various wall twist structures. The Bloch curve wall structure was inferred from the measured velocity-momentum data, with the Bloch curve nucleation threshold being different for the two surfaces of an ion-implanted film. This was indicated by the transition between the branches for one and two Bloch curves in the experimental velocity-momentum relation.