Magnetic anisotropy driven by enhanced spin-orbital coupling of sp metal Bi on Au /Si(111) root3 surface

Realization of magnetic properties from non-magnetic elements is an interesting issue recently. Using first-principles calculations based on DFT, we study of 1/3 monolayer Bi-covered Au/Si(111) surface and find that such system can be magnetic remarkably. Our further analysis reveals that the large spin-orbit coupling of Bi (p_x, p_y) multi-orbitals at the Fermi level leads to an occupancy disparity between spin channels. And this occupancy disparity will break Krammers degeneracy, resulting in a non-magnetic to significant ferromagnetic phase transition. Moreover, the relatively large and anisotropic Rashba splitting at the interface damps the in-plane ferromagnetism, giving rise to an exceptionally large magnetic anisotropy energy up to 6.5 meV (with M_z/M_x,y~3). Our studies provide a potential candidate system for achieving an intrinsic quantum anomalous Hall effect with temperature up to 70 K.