Magnetic properties of lanthanide adatoms on graphene*

Individual magnetic adatoms on surfaces may exhibit long-lived spin quantum states that can be efficiently manipulated and detected, making such systems promising materials for ultrahigh-density magnetic information storage and quantum logic devices. Rare-earth adatoms on graphene are of particular interest since strong spin-orbit coupling of lanthanides may lead to a large anisotropy barrier while the absence of a nuclear spin in ¹²C is expected to increase the coherence time of adatom spin states. Further, the properties of the system may be controlled by gating. Here, we study electronic structure and magnetic properties of rare-earth adatoms on graphene using combination of density functional theory (DFT), ab initio multireference quantum chemistry methods, and effective spin Hamiltonian technique. Preferred adsorption sites and atomic coordinates are determined using DFT calculations in the supercell geometry.  The resulting structures are then used to build cluster models, and low-energy electronic spectra and magnetic interactions are calculated using quantum chemistry methods. Ab initio effective spin Hamiltonians are then constructed and different mechanisms for magnetic relaxation and decoherence are discussed.