Skyrmion pinning by disk-shaped defects

TL;DR

This paper investigates how disk-shaped defects can precisely pin skyrmions, revealing fundamental differences between thin-wall and thick-wall skyrmions, and how size and material parameters influence pinning behavior and stability.

Contribution

It provides a detailed analysis of skyrmion pinning mechanisms by disks, highlighting the importance of skyrmion type, disk size, and material properties for controlled manipulation.

Findings

Skyrmion pinning depends on disk size and skyrmion type.

Thin-wall and thick-wall skyrmions respond differently to material parameters.

Thermal effects can depin skyrmions following an Arrhenius law.

Abstract

High precision skyrmion pinning by an intentionally created magnetic structure is important in skyrmion manipulation. Here, we consider skyrmion pinning by various types of disks. Among other findings, we clarify that, in terms of pinning position and pinning potential landscape, one needs to distinguish thin-wall skyrmions from thick-wall skyrmions because of fundamental differences. A skyrmion wall prefers areas with a weaker exchange stiffness, a larger DMI constant, or a smaller magnetic anisotropy while a skyrmion core experiences only the magnetic anisotropy, not exchange stiffness and DMI. Depending on disk type, skyrmion type, and the relative size of the disk (to skyrmion), a skyrmion can be pinned at the symmetric (center) or asymmetric (off-center) point of a disk. In case a skyrmion is pinned by a local energy minimum, thermal agitation can depin the skyrmion, and the pinning lifetime follows an Arrhenius law. Interestingly, when the disk size is comparable to the skyrmion size, the skyrmion deforms greatly such that the skyrmion will shrink or expand to fill the whole disk. These findings should be important for skyrmion manipulations.