Emergence of Sizeable Interfacial Dzyaloshinskii-Moriya Interaction at Cobalt/Fullerene Interface

The interfacial Dzyaloshinskii-Moriya interaction (iDMI) originating from a heavy-metal/ferromagnet (FM) interface plays a crucial role in stabilizing chiral spin textures in magnetic multilayers. Recently, graphene based on the low-spin-orbit-coupling (SOC) element carbon (C) has shown a significant iDMI owing to the Rashba SOC when deposited on top of Co. A similar enhanced SOC has been reported earlier for other C allotropes, namely fullerene (C60) and carbon nanotubes, and a sizeable DMI can be expected to emerge from them. In this context, we elucidate the magnetization-reversal mechanism, the domainwall (DW) dynamics, and the strength of the iDMI in a Pd(4.0 nm)/Co(0.5 nm)/C60(tC60)/Pd(2.0 nm) system with varying tC60. The field-induced DW velocity measured in the creep region shows a DW velocity 2 orders of magnitude higher for a sample with 1.6 nm of C60, due to a lower depinning field and spin-dependent hybridization at the Co/C60 interface. Further, DMI measurements performed by use of the asymmetric DW expansion method exhibit a systematic increase in the iDMI from -0.07 to -0.46 mJ/m2 with an increase in tC60. Such an enhanced iDMI turns an achiral Bloch wall into a chiral Neel wall. The emergence of a finite DMI (DCo/C60 similar to - 0.11 mJ/m2) from the Co/C60 interface is particularly encouraging for the use of C-based materials in chiral-DW-based device applications.

Automated summary

The strength of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) and the dynamics of domain walls (DWs) were investigated in a Pd/Co/C60/Pd system. The iDMI was found to increase from -0.07 to -0.46 mJ/m2 with increasing C60 thickness, transforming an achiral Bloch wall into a chiral Neel wall. This is significant for the use of carbon-based materials in chiral-DW-based device applications.