magnetic bubble domains are propagated in a magnetic medium in a desired direction using in - plane magnetic fields which are time varying but which have no spatial gradients . in applications such as information storage , the need for conventional propagation structures , such as offset conductor loops , patterned magnetic elements , and patterned ion implantation regions is reduced . bubble domains having unwinding pairs of bloch lines in their wall magnetization can be moved by applying appropriate in - plane magnetic fields , without the need for spatial gradients or variations in the magnetic field normal to the plane of the magnetic medium . the continuous movement of these bubble domains occurs by a cyclic process where the bloch lines switch between two configurations , in an asymmetric way in response to the time varying in - plane field .