Chiral damping of magnetic domain walls

TL;DR

This paper reports the discovery of a chiral damping mechanism in magnetic domain walls caused by structural inversion asymmetry, which is dissipative and distinct from the conservative Dzyaloshinskii-Moriya interaction, impacting magnetic device design.

Contribution

It introduces the concept of chiral damping as a new physical phenomenon in magnetic materials, differentiating it from DMI through its dissipative nature and experimental identification.

Findings

Chiral damping observed in Pt/Co/Pt trilayers.

Chiral damping coexists with DMI but has different physical origins.

Experimental method distinguishes chiral damping from DMI using in-plane magnetic fields.

Abstract

Structural symmetry breaking in magnetic materials is responsible for a variety of outstanding physical phenomena. Examples range from the existence of multiferroics, to current induced spin orbit torques (SOT) and the formation of topological magnetic structures. In this letter we bring into light a novel effect of the structural inversion asymmetry (SIA): a chiral damping mechanism. This phenomenon is evidenced by measuring the field driven domain wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The difficulty in evidencing the chiral damping is that the ensuing DW dynamics exhibit identical spatial symmetry to those expected from the Dzyaloshinskii-Moriya interaction (DMI). Despite this fundamental resemblance, the two scenarios are differentiated by their time reversal properties: while DMI is a conservative effect that can be modeled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing to distinguish the physical mechanism. The observation of the chiral damping, not only enriches the spectrum of physical phenomena engendered by the SIA, but since it can coexists with DMI it is essential for conceiving DW and skyrmion devices.