Domain‐Wall Circulation Gating and Pinning via Compositional Engineering of Cylindrical Nanowires

Abstract

ABSTRACT Spintronic devices based on cylindrical magnetic nanowires have been proposed as a route toward three–dimensional (3D) information storage and processing by harnessing the controlled motion of domain walls (DWs). In this geometry, the Bloch‐point wall (BPW) is the characteristic DW type. It features a curling of magnetization around a Bloch Point singularity, a topology that has been predicted to enable propagation at high speed without undergoing a Walker breakdown. We demonstrate that compositional modulations of larger magnetization, which host spontaneous curling states while the rest of the wire remains axial, fulfil a dual role: they act as deterministic pinning sites and as active gates for BPW circulation. Combining magnetic transmission X–ray microscopy and micromagnetic simulations, we reveal that DW–modulation interactions are the result of a superposition of long–range magnetostatic repulsion and short–range, circulation–dependent exchange contributions: parallel circulation produces an attractive well, while opposite circulation generates a repulsive barrier. This results in DW pinning at or near a compositional modulation. A DW's internal circulation can be inverted upon traversing a modulation, enabling on–demand switching of its circulation state. This dual mechanism demonstrates that both DW position and circulation can be tuned in a controlled manner, with potential implications for multistate spintronic devices.