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

Abstract

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.