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Magnetic vortex chirality switching in Permalloy nanowires with asymmetric notches

We have investigated the motion of vortex domain walls passing across non symmetric triangular notches in single Permalloy nanowires. We have measured hysteresis cycles using the focused magneto-optical Kerr effect before and beyond the notch, which allowed to probe beyond the notch the occurrence probability of clockwise (CW) and counter-clockwise (CCW) walls in tail-to-tail (TT) and head-to-head (HH) configurations. We present experimental evidence of chirality flipping provided by the vortex -- notch interaction. With a low exit angle the probability of chirality flipping increases and here with the lowest angle of 15$^o$ the probability of propagation of the energetically favored domain wall configuration (CCW for TT or CW for HH walls) is $\approx 75\%$. Micromagnetic simulations reveal details of the chirality reversal dynamics.