Magnetic imaging of the pinning mechanism of asymmetric transverse domain walls in ferromagnetic nanowires

The pinning of asymmetric transverse magnetic domain walls by constrictions and protrusions in thin permalloy nanowires is directly observed using the Fresnel mode of magnetic imaging. Different domain wall (DW)/trap configurations are initialized using in situ applied magnetic fields, and the resulting configurations are imaged both at remanence and under applied fields. The nature of the chirality dependent pinning potentials created by the traps is clearly observed. The effect of the asymmetry of the DW is discussed. Micromagnetic simulations are also presented, which are in excellent agreement with the experiments