Probing the Dzyaloshinskii-Moriya interaction in CoFeB ultrathin films using domain wall creep and Brillouin light spectroscopy

TL;DR

This study compares two experimental techniques to measure the Dzyaloshinskii-Moriya interaction in ultrathin CoFeB films, revealing qualitative agreement but highlighting the need for improved models.

Contribution

It provides a comparative analysis of domain wall creep and Brillouin light spectroscopy methods for quantifying DMI in ultrathin magnetic films.

Findings

DMI estimates from different methods only qualitatively agree

Brillouin light spectroscopy measures spin wave non-reciprocity

Domain wall creep measurements relate to in-plane field effects

Abstract

We have characterized the strength of the interfacial Dyzaloshinskii-Moriya interaction (DMI) in ultrathin perpendicularly magnetized CoFeB/MgO films, grown on different underlayers of W, TaN, and Hf, using two experimental methods. First, we determined the effective DMI field from measurements of field-driven domain wall motion in the creep regime, where applied in-plane magnetic fields induce an anisotropy in the wall propagation that is correlated with the DMI strength. Second, Brillouin light spectroscopy was employed to quantify the frequency non-reciprocity of spin waves in the CoFeB layers, which yielded an independent measurement of the DMI. By combining these results, we show that DMI estimates from the different techniques only yield qualitative agreement, which suggests that open questions remain on the underlying models used to interpret these results.