Thermally Activated Processes for Ferromagnet Intercalation in Graphene-Heavy Metal Interfaces

TL;DR

This paper demonstrates a controlled method for intercalating ferromagnetic metals beneath graphene on heavy metal substrates, enabling high-quality heterostructures for advanced spintronic applications.

Contribution

It introduces a nanoscale control technique for thermally activated ferromagnetic intercalation under graphene, with detailed analysis of activation energies and optimal temperatures.

Findings

Ferromagnetic atoms form 3D clusters on graphene surface.

Thermal annealing induces 2D diffusion of metals beneath graphene.

Complete intercalation occurs at specific temperatures depending on the substrate.

Abstract

The development of graphene (Gr) spintronics requires the ability to engineer epitaxial Gr heterostructures with interfaces of high quality, in which the intrinsic properties of Gr are modified through proximity with a ferromagnet to allow for efficient room temperature spin manipulation or the stabilization of new magnetic textures. These heterostructures can be prepared in a controlled way by intercalation through graphene of different metals. Using photoelectron spectroscopy (XPS) and Scanning Tunneling Microscopy (STM), we achieve a nanoscale control of thermal activated intercalation of homogeneous ferromagnetic (FM) layer underneath epitaxial Gr grown onto (111)-oriented heavy metal (HM) buffers deposited in turn onto insulating oxide surfaces. XPS and STM demonstrate that Co atoms evaporated on top of Gr arrange in 3D clusters, and, upon thermal annealing, penetrate through and diffuse below Gr in a 2D fashion. The complete intercalation of the metal occurs at specific temperatures depending on the type of metallic buffer. The activation energy and the optimum temperature for the intercalation processes are determined. We describe a reliable method to fabricate and characterize in-situ high quality Gr-FM/HM heterostructures enabling the realization of novel spin-orbitronic devices that exploits the extraordinary properties of Gr.