Effects of antiferromagnetic coupling and pinning on domain wall dynamics in synthetic ferrimagnets

TL;DR

This paper investigates how antiferromagnetic coupling and pinning influence domain wall dynamics in synthetic ferrimagnets, revealing key effects on depinning fields, anisotropy, and mobility, with implications for spintronic device performance.

Contribution

It provides a comprehensive analysis of domain wall dynamics in synthetic ferrimagnets, introducing a novel method to measure effective spin-orbit torques and exploring the effects of Tb layer variations.

Findings

Increased Tb thickness reduces saturation magnetization and enhances depinning field.

Complete removal of Tb layer increases anisotropy and domain wall pinning.

Proposed a new approach to measure effective spin-orbit torques via depinning transitions.

Abstract

Domain wall (DW) dynamics in antiferromagnetic (AFM) systems offer the advantages over their ferromagnetic counterparts of having faster and more energy efficient manipulation due to the absence of net magnetization, leading to reduced magnetic crosstalk and improved performance in spintronic devices. A comprehensive analysis of DW dynamics across regimes such as creep, depinning, and flow is well established in ferromagnetic systems but remains lacking in AFM-coupled systems. In this study, we explore the nature of DW dynamics in synthetic ferrimagnetic multilayers composed of Pt|Co|Tb|Al for different Tb thickness, focusing on the underlying pinning parameters, and on the different regimes of DW dynamics driven by spin-orbit torques (SOTs). We find that due to the AFM coupling between Co and Tb, the magnetic moment of Tb increases with Tb thickness resulting in a reduced saturation magnetization and an enhanced depinning field. The DW disorder interaction is found to vary weakly with the AFM coupling between Co and Tb, while the complete withdrawal of the Tb layer strongly increases the anisotropy and the DW pinning. Furthermore, we propose a novel approach to measure effective SOTs by comparing depinning transitions in current and field-induced DW motion. This research reveals new insights into DW dynamics in coupled AFM systems, highlighting enhancements in mobility through optimized SOTs and pinning landscapes.