Domain wall pinning and potential landscapes created by constrictions and protrusions in ferromagnetic nanowires

The potential experienced by transverse domain walls (TDWs) in the vicinity of asymmetric constrictions or protrusions in thin Permalloy nanowires is probed using spatially resolved magneto-optical Kerr effect measurements. Both types of traps are found to act as pinning centers for DWs. The strength of pinning is found to depend on the trap type as well as on the chirality of the incoming DW; both types of traps are seen to act either as potential wells or potential barriers, also depending on the chirality of the DW. Micromagnetic simulations have been performed that are in good qualitative agreement with the experimental results.