Magnetic properties of 4f adatoms on graphene: Density functional theory investigations

Rare-earth atoms on top of 2D materials represent an interesting platform with the prospect of tailoring the magnetic anisotropy for practical applications. Here, we investigate the ground state and magnetic properties of selected $4f$ atoms deposited on a graphene substrate in the framework of the $\mathrm{DFT}+U$ approach. The inherent strong spin-orbit interaction in conjunction with crystal field effects acting on the localized $4f$ shells results in a substantial magnetic anisotropy energy (tens of meVs), whose angular dependence is dictated by the ${C}_{6v}$ symmetry of the graphene substrate. We obtain the crystal-field parameters and investigate spin-flip events via quantum tunneling of magnetization in the view of achieving a protected quantum-spin behavior. Remarkably, the large spin and orbital moments of the open $4f$ shells (Dy, Ho, and Tm) generate a strong magnetoelastic coupling which provides more flexibility to control the magnetic state via the application of external strain.