Study on the trapping of domain wall in an Ni-Fe nanowire with a constricted area

This paper reports the study on magnetization reversal in a 10-nm-thick Ni-Fe nanowire with a constricted area in order to understand the domain wall trapping in the nanowire. The micromagnetics simulation indicates that the shape of the hysteresis loop in the nanowire is stepped square. It also shows that the domain wall moves from the edge of a notch connected to the wider nanowire and is partly pinned at the most constricted portion of the nanowire, and further annhilates as the magnetic field is varied from positive to negative or vice-versa. The magnetic-field sweeping magnetic-force microscopy measurements verified these predictions at various points within the nanowire by means of the phase (the stray field) versus magnetic-field curves. On the basis of these results, it is evident that a dominant factor in the magnetization reversal of the nanowire is mainly the domain wall motion within the nanowire, and that the domain wall is trapped in the constricted area because of the difference of coercivity between the narrower and wider nanowires.