Heisenberg Exchange and Dzyaloshinskii-Moriya Interaction in Ultrathin CoFeB Single and Multilayers

TL;DR

This study uses Brillouin Light Scattering to analyze spin waves in ultrathin CoFeB layers, revealing the effects of adjacent heavy metals on exchange interactions and Dzyaloshinskii-Moriya interaction, crucial for spintronic device design.

Contribution

It provides a detailed experimental analysis of exchange interactions and DMI in CoFeB layers with different heavy metal interfaces, highlighting their impact on spin-wave properties.

Findings

Large DMI in CoFeB/Pt layers

Negligible DMI in CoFeB/W layers

Influence of dipolar interactions on dispersion and exchange parameters

Abstract

We present results of the analysis of Brillouin Light Scattering (BLS) measurements of spin waves performed on ultrathin single and multirepeat CoFeB layers with adjacent heavy metal layers. From a detailed study of the spin-wave dispersion relation, we independently extract the Heisenberg exchange interaction (also referred to as symmetric exchange interaction), the Dzyaloshinskii-Moriya interaction (DMI, also referred to as antisymmetric exchange interaction), and the anisotropy field. We find a large DMI in CoFeB thin films adjacent to a Pt layer and nearly vanishing DMI for CoFeB films adjacent to a W layer. Furthermore, the residual influence of the dipolar interaction on the dispersion relation and on the evaluation of the Heisenberg exchange parameter is demonstrated. In addition, an experimental analysis of the DMI on the spin-wave lifetime is presented. All these parameters play a crucial role in designing skyrmionic or spin-orbitronic devices.