Tunable Magnetism of Transition Metal Nanostructures by Hydrogenated Graphene

Controlling magnetism of transition metal atoms by pairing with $\pi$ electronic states of graphene is intriguing. Herein, through first - principle computation we explore the possibility of switching magnetization by forming the tetrahedral $sp^3$ - metallic $d$ hybrid bonds. Graphene multilayers capped by single - layer cobalt atoms can transform into the $sp^3$ - bonded diamond films upon the hydrogenation of the bottom surface. While the conversion is favored by hybridization between the $sp^3$ dangling bonds and metallic $d_{z^2}$ states, such a strong hybridization can lead to the reorientation of magnetization easy axis of cobalt adatoms in plane to perpendicular. The further investigations identify that this anisotropic magnetization even can be modulated upon the change in charge carrier density, suggesting the possibility of an electric - field control of magnetization reorientation. These results provide a novel alternative that would represent tailoring magnetism by means of degree of the interlayer hybrid bonds in the layered materials.