Domain-Wall Pinning by Local Control of Anisotropy in Pt/Co/Pt strips

TL;DR

This study combines theoretical modeling and experimental techniques to control and analyze magnetic domain wall pinning in Pt/Co/Pt strips through local anisotropy variations, enabling tunable magnetic properties.

Contribution

It introduces a method to engineer domain wall pinning by locally controlling anisotropy via focused ion beam irradiation and thickness adjustments, with quantitative validation.

Findings

Anisotropy steps create energy barriers for domain walls.

Focused ion beam irradiation effectively tunes anisotropy.

Thinner Co layers increase anisotropy and pinning range.

Abstract

We theoretically and experimentally analyze the pinning of a magnetic domain wall (DW) at engineered anisotropy variations in Pt/Co/Pt strips with perpendicular magnetic anisotropy. An analytical model is derived showing that a step in the anisotropy acts as an energy barrier for the DW. Quantitative measurements are performed showing that the anisotropy can be controlled by focused ion beam irradiation with Ga ions. This tool is used to experimentally study the field-induced switching of nanostrips which are locally irradiated. The boundary of the irradiated area indeed acts as a pinning barrier for the domain wall and the pinning strength increases with the anisotropy difference. Varying the thickness of the Co layer provides an additional way to tune the anisotropy, and it is shown that a thinner Co layer gives a higher starting anisotropy thereby allowing tunable DW pinning in a wider range of fields. Finally, we demonstrate that not only the anisotropy itself, but also the width of the anisotropy barrier can be tuned on the length scale of the domain wall.