Kinetic and Static Domain-Wall Pinning at Notches on Ferromagnetic Nanowires

We investigate the domain wall (DW) pinning and depinning processes at notches of ferromagnetic nanowires by means of micromagnetic calculation. Two distinct pinning mechanisms are examined-the kinetic pinning for a moving DW to be trapped at a notch and the static depinning for a trapped DW to move from the notch. Interestingly, the kinetic pinning field is revealed to be noticeably smaller than the static depinning field. The DW energy landscapes around the notch visualize that the kinetic DW motion bypasses the lowest energy state, from which the static depinning field is determined. This phenomenon is basically equivalent to the kinetic and static friction processes in classical mechanics.