Current-driven domain wall motion in magnetic wires with asymmetric   notches
  Current-driven domain wall (DW) motion in magnetic wires with asymmetric notches was investigated by means of magnetic force microscopy. It was found that the critical current density necessary for the current-driven DW motion depended on the propagation direction of the DW. The DW moved more easily in the direction along which the slope of the asymmetric notch was less inclined. 
A. Himeno, S. Kasai, and T. Ono