Thermal spin wave noise as a probe for the Dzyaloshinkii-Moriya interaction

TL;DR

This paper introduces a novel, qualitative method using thermal spin wave noise detected by NV center relaxometry to determine the sign and nature of Dzyaloshinskii-Moriya interaction in thin magnetic films, providing new insights into magnetic states.

Contribution

It presents a new qualitative approach to measure DMI sign and type through thermal spin wave noise, complementing existing quantitative techniques.

Findings

Noise amplitude indicates DMI sign due to non-reciprocal spin wave dispersion

Skyrmion noise distribution reveals Ne9el/Bloch character

Method validated both numerically and experimentally

Abstract

Interfacial Dzyaloshinkii-Moriya interaction (DMI) is a key ingredient in the stabilization of chiral magnetic states in thin films. Its sign and strength often determine crucial properties of magnetic objects, like their topology or how they can be manipulated with currents. A few experimental techniques are currently available to measure DMI quantitatively, based on the study of domain walls, spin waves, or spin-orbit torques. In this work, we propose a qualitative variant of spin wave methods. We rely on magnetic noise from confined thermal spin waves in domain walls and skyrmions in perpendicularly magnetized thin films, which we probe with scanning NV center relaxometry. We show both numerically and experimentally that the sign of the DMI can be inferred from the amplitude of the detected noise, which is affected by the non-reciprocity in the spin wave dispersion. Furthermore, we also demonstrate that the noise distribution around the contour of magnetic skyrmions reveals their N\'eel/Bloch nature, giving therefore also insight into the strength of DMI involved in their stabilization.