The effect of geometrical confinement and chirality on domain wall pinning behavior in planar nanowires

We investigate the domain wall pinning behavior in Permalloy nanowires using experimental measurements and micromagnetic simulations. Planar nanowire structures were fabricated by electron beam lithography followed by thin-film deposition via thermal evaporation. The magnetization switching behavior of individual nanowires was measured using the magneto-optical Kerr effect. For symmetrical pinning structures such as the junction between a wider domain wall injection pad and a narrower nanowire, the domain wall depinning field increases as the wire width decreases, with the depinning field increasing rapidly for wires widths below 400 nm. For domain wall pinning at asymmetrical structures such as a notch, the magnitude of the depinning field appears relatively insensitive to notch geometry for triangular and rectangular notch structures, compared to the influence of the wire width. The domain wall depinning field from triangular notches increases as notch depth increases although this increase levels off at notch depths greater than approximately 60% wire width. The nature of domain wall pinning at asymmetrical notch structures is also sensitive to domain wall chirality.