Direct measurement of interfacial Dzyaloshinskii-Moriya interaction in X/CoFeB/MgO heterostructures with a scanning-NV magnetometer

TL;DR

This study uses a scanning NV magnetometer to directly measure the interfacial Dzyaloshinskii-Moriya interaction in ultrathin CoFeB/MgO films with different heavy metal underlayers, revealing local variations and chiral spin textures.

Contribution

It demonstrates a novel local measurement technique for DMI in magnetic heterostructures using a scanning NV magnetometer, providing insights into nanoscale magnetic order.

Findings

Detected deviations from Bloch DW profiles indicating positive DMI.

Observed local variations of DMI within single samples.

Confirmed DMI's role in stabilizing chiral spin textures.

Abstract

The Dzyaloshinskii-Moriya Interaction (DMI) has recently attracted considerable interest owing to its fundamental role in the stabilization of chiral spin textures in ultrathin ferromagnets, which are interesting candidates for future spintronic technologies. Here we employ a scanning nano-magnetometer based on a single nitrogen-vacancy (NV) defect in diamond to locally probe the strength of the interfacial DMI in CoFeB/MgO ultrathin films grown on different heavy metal underlayers X=Ta,TaN, and W. By measuring the stray field emanating from DWs in micron-long wires of such materials, we observe deviations from the Bloch profile for TaN and W underlayers that are consistent with a positive DMI value favoring right-handed chiral spin structures. Moreover, our measurements suggest that the DMI constant might vary locally within a single sample, illustrating the importance of local probes for the study of magnetic order at the nanoscale.