IEEE Magn. Lett.

Previous experiments have shown that perpendicular magnetic anisotropy (PMA) in tri-layers consisting of a CoFeB layer, an MgO layer, and a nonmagnetic metal (NM) layer depends strongly on whether the CoFeB layer was grown on the top of NM layer or was capped by a NM layer. In this work, we studied the physical origin of this phenomenon through firstprinciples calculations. We took MgO/CoFe/Ta and Ta/CoFe/MgO as model structures and analyzed the magnetic anisotropy energy (MAE) therein. We found that the “substrate/Ta/CoFe/MgO” structure had a notably higher MAE than the “substrate/MgO/CoFe/Ta” structure. This difference results mainly from different stresses in the Ta layers, and the latter gives rise to a difference in the hybridization strength of in-plane orbits ( xy d , 2 2 x y d  , x p and y p ). We also found that the p orbital hybridization in the Ta layers contributes significantly to the PMA in both structures.

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2019-11-12