Magnetic vortex chirality switching in Permalloy nanowires with asymmetric notches

TL;DR

This paper investigates how asymmetric notches in Permalloy nanowires influence vortex domain wall chirality switching, combining experimental measurements and micromagnetic simulations to reveal the conditions that favor chirality flipping.

Contribution

It provides experimental evidence and simulation insights into vortex chirality flipping caused by asymmetric notches in nanowires, a novel mechanism for domain wall control.

Findings

Chirality flipping probability increases with lower exit angles.

At 15° exit angle, 75% of domain walls maintain energetically favored chirality.

Micromagnetic simulations detail the reversal dynamics.

Abstract

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.