Nature of Interfacial Dzyaloshinskii-Moriya Interactions in Graphene/Co/Pt(111) Multilayer Heterostructures

TL;DR

This study uses DFT calculations to analyze interfacial Dzyaloshinskii-Moriya interactions in Graphene/Co/Pt multilayers, revealing decoupled interfaces, chirality inversion by Graphene, and the complex nature of DMI beyond simple models.

Contribution

It provides a detailed spectral analysis showing that DMI arises from SOC-split hybrid bands, challenging simplified single-band models like Rashba DMI.

Findings

DMI at both interfaces are decoupled for n ≥ 3

Graphene inverts DMI chirality and reduces overall DMI

DMI is dominated by Pt's strong SOC and involves SOC-split hybrid bands

Abstract

DFT calculations within the generalized Bloch theorem approach show that interfacial Dzyaloshinskii-Moriya interactions (DMI) at both interfaces of Graphene/Co$_n$/Pt(111) multilayer heterostructures are decoupled for $n \geq 3$. Unlike the property of magnetocrystalline anisotropy for this system, DMI is not affected by stacking defects in the Co layer. The effect of Graphene (Gr) is to invert the chirality of the vaccum/Co interfacial DMI, overall reducing the DMI of the heterostructure, which is nevertheless dominated by the strong spin-orbit coupling (SOC) of Pt. A spectral analysis in the reciprocal space shows that DMI at both the Gr/Co and Co/Pt interfaces have the same nature, namely SOC-split hybrid bands of $d$-orbital character. This proves that a DMI model based on a single band, such the Rashba DMI model, is insuficient to describe the behaviour of this family of Gr-capped $3d/5d$ metal heterostructures.