Antiferromagnetic Domain Wall Control via the Surface Spin Flop in Fully Tunable Synthetic Antiferromagnets with Perpendicular Magnetic Anisotropy

TL;DR

This paper demonstrates a method to nucleate and stabilize antiferromagnetic domain walls in synthetic antiferromagnets with perpendicular magnetic anisotropy, enabling tunable and controllable AF domain wall states for spintronic applications.

Contribution

It introduces a novel approach to control AF domain walls in SAFs through interface engineering and surface spin flop stabilization, with experimental and micromagnetic validation.

Findings

Stable AF domain walls achieved in multilayer stacks.

Surface spin flop state can be controlled via layer thickness.

Fully tunable vertical AF domain walls without single crystal substrates.

Abstract

Antiferromagnetic (AF) domain walls have recently attracted revived attention, not only in the emerging field of AF spintronics, but also more specifically for offering fast domain wall velocities and dynamic excitations up to the terahertz frequency regime. Here we introduce an approach to nucleate and stabilize an AF domain wall in a synthetic antiferromagnet (SAF). We present experimental and micromagnetic studies of the magnetization reversal in [(Co/Pt)$_{X-1}$/Co/Ir]$_{N-1}$(Co/Pt)$_X$ SAFs, where interface induced perpendicular magnetic anisotropy (PMA) and AF interlayer exchange coupling (IEC) are completely controlled via the individual layer thicknesses within the multilayer stack. By combining strong PMA with even stronger AF IEC, the SAF reveals a collective response to an external magnetic field applied normal to the surface, and we stabilize the characteristic surface spin flop (SSF) state for an even number N of AF-coupled (Co/Pt)$_{X-1}$/Co multilayer blocks. In the SSF state our system provides a well-controlled and fully tunable vertical AF domain wall, easy to integrate as no single crystal substrates are required and with uniform 2D-magnetization in the film plane for further functionalization options, such as for example lateral patterning via lithography.