Spin and orbital magnetic moments and spin anisotropy energies of light rare earth atoms embedded in graphene: A first-principles study

Abstract

The geometries, electronic structures, spin magnetic moments (SMMs), orbital magnetic moments (OMMs) and spin anisotropy energies (SAEs) of light rare earth atoms (La, Ce, Pr, Nd, Pm, Sm, Eu, and Gd) embedded in graphene were studied by using first-principles calculations based on Density Functional Theory (DFT). The spin-orbital coupling effect was taken into account and GGA+U method was adopted to describe the strongly localized and correlated 4f electrons. There is a significant deformation of the graphene plane after doping and optimization. The deformation of Gd doped graphene is the largest, while Eu the smallest. The results show that the valence is +3 for La, Ce, Pr, Nd, Pm, Sm and Gd, and +2 for Eu. Except Eu and Gd, there are obvious OMMs. When the spin is in the Z direction, the OMMs are −0.941μB, −1.663μB, −3.239μB, −3.276μB and −3.337μB for Ce, Pr, Nd, Pm and Sm, respectively, and point the opposite direction of SMMs. All the doped systems except Gd show considerable SAEs. For Ce, Pr, Nd, Pm, Sm, and Eu, the SAEs are −0.928meV, 20.941meV, −8.848meV, 7.855meV, 75.070meV and 0.810meV, respectively. When the spin orientation is different, different orbital angular moments lead to apparent charge density difference of the 4f atoms, which can also explain the origin of SAEs.