Angular dependence of the depinning field for head-to-head domain walls at constrictions

The angular dependence of the depinning field of vortex and transverse domain walls is determined experimentally for NiFe rings with nanometer size constrictions. From the angular dependence, we are able to deduce the potential landscape caused by the constriction and seen by the wall. The potential minimum for transverse walls is at the notch position so that these walls are pinned symmetrically inside the constriction. Vortex walls are pinned at a position adjacent to the constriction and this position can be determined from the angular variation of the depinning fields. Good agreement with the results of micromagnetic simulations is obtained. (c) 2007 American Institute of Physics.