Enhanced magnetoresistance and pinning–depinning processes of vortex domain walls in ferromagnetic nanowires

We have investigated the pinning–depinning processes of vortex domain walls (VDW) in Permalloy nanowires with asymmetric triangular notches by means of magnetoresistance measurements and micromagnetic simulations. Through a model based on the anisotropic magnetoresistance (AMR) and the magnetization structure obtained from simulations, the magnetoresistance when the VDW passes stretched through the notch was calculated. Besides the depinning field, as it is known, also the magnetoresistance drop depends on the domain wall chirality. Measurements show that the resistance drop for clockwise (CW) chirality is  ≈180 m$\Omega$ (38%) larger than for the counterclockwise (CCW) chirality. From the VDW resistance calculations it becomes clear which domain wall parameters, like domain wall structure, chirality and wall width, play a role on the magnetoresistance. These results offer an additional route to better controlling the VDW motion, which can be beneficial to applications. (paper)