<i>In situ</i> visualization of chemical interdiffusion phenomena in ultrathin graphene intercalated Co/Pt heterostructures for spintronics

Graphene-based magnetic epitaxial heterostructures, where an ultrathin layer of a ferromagnetic metal is sandwiched between a heavy metal and a graphene monolayer, have been widely studied due to their easily tunable interfacial driven spin-orbit interactions. The interplay between orbital hybridization and symmetry breaking at the interfaces in systems like graphene/Co grown epitaxially on Pt results in enhanced perpendicular magnetic anisotropy and sizeable antisymmetric exchange interaction, enabling the possibility to stabilize thermally stable chiral spin textures and their manipulation with external stimuli. However, in order to properly exploit the functionality of such heterostructures, the crystal structure, composition, and integrity of the ultrathin ferromagnetic metallic layer must be understood down to the atomic level. For this aim, the characterization of thermally activated atomic processes taking place during growth, along with changes likely taking place during future device performance derived from Joule heating, is a must. In this work, we use atomic resolution electron microscopy and spectroscopy techniques to investigate thermally activated interdiffusion phenomena at Co/Pt interfaces in the range of 300–773 K. We show how significant alloying takes place at the Co/Pt interface for higher annealing temperatures. Such interdiffusion affects the magnetic properties of the layers, enhancing the layer coercivity. Such direct visualization of the thermally induced interdiffusion effects offers a pathway for optimizing graphene-based magnetic epitaxial systems for robust device integration.