Low-energy magnetic states of Tb adatom on graphene
Year: 2024
Type: article
Abstract: Electronic structure and magnetic interactions of a Tb adatom on graphene are investigated from first principles using combination of density functional theory and multiconfigurational quantum chemistry techniques including spin–orbit coupling (SOC) . We determine that the six-fold symmetry hollow site is the preferred adsorption site and investigate electronic spectrum for different adatom oxidation states including Tb3+, Tb2+, Tb1+, and Tb0. For all charge states, the Tb 4 f 8 configuration is retained with other adatom valence electrons being distributed over 5 d x y , 5 d x 2 + y 2 , and 6 s / 5 d 0 single-electron orbitals. We find strong intra-site adatom exchange coupling that ensures that the 5 d 6 s spins are parallel to the 4f spin. For Tb3+, the energy levels can be described by the J = 6 multiplet split by the graphene crystal field (CF). For other oxidation states, the interaction of 4f electrons with spin and orbital degrees of freedom of 6 s 5 d electrons in the presence of SOC results in the low-energy spectrum composed closely lying effective multiplets that are split by the graphene CF. Stable magnetic moment is predicted for Tb3+ and Tb2+ adatoms due to uniaxial magnetic anisotropy and effective anisotropy barrier around 440 cm−1 controlled by the temperature assisted quantum tunneling of magnetization through the third excited doublet. On the other hand, in-plane magnetic anisotropy is found for Tb1+ and Tb0 adatoms. Our results indicate that the occupation of the 6 s 5 d orbitals can dramatically affect the magnetic anisotropy and magnetic moment stability of rare earth adatoms.
Institution: University of Nebraska at Kearney
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,165
OpenAlex ID: W4404130226