Large perpendicular magnetic anisotropy of transition metal dimers driven by polarization switching of a two-dimensional ferroelectric In 2 Se 3 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 In 2 Se 3 (In 2 Se 3 -CoOs, In 2 Se 3 -OsCo, In 2 Se 3 -CoCo and In 2 Se 3 -OsOs) using first-principles calculations. We find that the Co-Os dimer in In 2 Se 3 -CoOs has a total magnetic anisotropy energy (MAE) of ∼40 meV. The MAE arising from the Os atom in In 2 Se 3 -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 In 2 Se 3 -CoOs and induced in In 2 Se 3 -OsCo, In 2 Se 3 -CoCo and In 2 Se 3 -OsOs by the ferroelectric polarization reversal of In 2 Se 3 . We demonstrate that the enlargement of exchange splitting of d xy /d x 2 - y 2 and d xz /d yz orbitals for Os atoms in In 2 Se 3 -OsOs, Co atom in In 2 Se 3 -CoOs and Os and Co atoms in In 2 Se 3 -OsCo is responsible for the increase of MAE; while, for the upper Co atom in In 2 Se 3 -CoCo and the Os atom in In 2 Se 3 -CoOs, the energy rise of the d z 2 orbital owing to the change of the crystal field effect by the reversal of ferroelectric polarization results in the increase of MAE.