Effect of Fe-O distance on magnetocrystalline anisotropy energy at the Fe/MgO(001) interface

We report first-principles calculations on the magnetocrystalline anisotropy energy (MAE) of an Fe monolayer sandwiched by MgO. We found that by increasing the interlayer distance between Fe and O by about 8% from its equilibrium value, the perpendicular interfacial magnetic anisotropy can be enhanced as high as 2.75 erg/cm², which is three times larger than that at the equilibrium distance. The analysis of MAE based on the second-order interactions of the spin-orbit coupling shows that the energy position of the majority-spin d_z2 orbital is of central importance in determining MAE. Our results suggest that increasing the Fe-O distance in the Fe/MgO system is an important material-design direction for high-performance magnetic memories.