Large perpendicular magnetic anisotropy of transition metal dimers driven by polarization switching of a two-dimensional ferroelectric In₂Se₃ substrate

Large perpendicular magnetic anisotropy (MA) is highly desirable for realizing atomic-scale magnetic data storage which represents the ultimate limit of the density of magnetic recording. In this work, we study the MA of transition metal dimers Co-Os, Co-Co and Os-Os adsorbed on two-dimensional ferroelectric In₂Se₃ (In₂Se₃-CoOs, In₂Se₃-OsCo, In₂Se₃-CoCo and In₂Se₃-OsOs) using first-principles calculations. We find that the Co-Os dimer in In₂Se₃-CoOs has a total magnetic anisotropy energy (MAE) of ∼40 meV. The MAE arising from the Os atom in In₂Se₃-CoOs is up to ∼60 meV. Such large MAE is attributed to the high spin-orbit coupling constant and the onefold coordination of the Os atom. In addition, perpendicular MA can be enhanced in In₂Se₃-CoOs and induced in In₂Se₃-OsCo, In₂Se₃-CoCo and In₂Se₃-OsOs by the ferroelectric polarization reversal of In₂Se₃. We demonstrate that the enlargement of exchange splitting of d_xy/d_x²-y² and d_xz/d_yz orbitals for Os atoms in In₂Se₃-OsOs, Co atom in In₂Se₃-CoOs and Os and Co atoms in In₂Se₃-OsCo is responsible for the increase of MAE; while, for the upper Co atom in In₂Se₃-CoCo and the Os atom in In₂Se₃-CoOs, the energy rise of the d_z² orbital owing to the change of the crystal field effect by the reversal of ferroelectric polarization results in the increase of MAE.