  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.
