Interfacial Dzyaloshinskii-Moriya interaction in perpendicularly-magnetized Pt/Co/AlO$_x$ ultrathin films measured by Brillouin light spectroscopy

TL;DR

This study investigates the interfacial Dzyaloshinskii-Moriya interaction in ultrathin Pt/Co/AlO$_x$ films using Brillouin light spectroscopy, revealing strong nonreciprocal spin wave propagation linked to chiral magnetic states.

Contribution

It provides quantitative measurement of interfacial DMI in ultrathin films and demonstrates its dominance over surface anisotropy effects.

Findings

Nonreciprocal spin wave propagation increases with decreasing Co thickness.

Interfacial DMI constant D_s = -1.7 ± 0.11 pJ/m measured.

Films below 1 nm support chiral states like skyrmions.

Abstract

Spin waves in perpendicularly-magnetized Pt/Co/AlO$_x$/Pt ultrathin films with varying Co thicknesses (0.6-1.2 nm) have been studied with Brillouin light spectroscopy in the Damon-Eshbach geometry. The measurements reveal a pronounced nonreciprocal propagation, which increases with decreasing Co thicknesses. This nonreciprocity is attributed to an interfacial Dzyaloshinskii-Moriya interaction (DMI), which is significantly stronger than asymmetries resulting from surface anisotropies for such modes. Results are consistent with an interfacial DMI constant $D_s = -1.7 \pm 0.11$ pJ/m, which favors left-handed chiral spin structures. This suggests that such films below 1 nm in thickness should support novel chiral states like skyrmions.