Interfacial electronic structure-modulated magnetic anisotropy in Ta/CoFeB/MgO/Ta multilayers

摘要

We have observed several unexpected phenomena when a trace amount of Fe atoms is deposited onto the CoFeB/MgO interface in Ta/CoFeB/MgO/Ta multilayers. With the nominal thickness of the introduced Fe atoms (t_(Fe)) varying from 0 to 0.1 A, the effective magnetic anisotropy energy (K_(eff)) of annealed multilayers is remarkably enhanced from 1.28 × 10~6 erg/cm~3 to 2.14 × 10~6 erg/cm~3. As t_(Fe) further increasing, the K_(eff) decreases and even becomes negative when t_(Fe) ＞ 1 A, indicating the change from perpendicular magnetic anisotropy to in-plane magnetic anisotropy. The analysis by X-ray photoelectron spectrometer reveals that the Fe atoms at annealed CoFeB/MgO interface show different electronic structures as t_(Fe) increasing, which combine with O atoms to form FeO_x (x＜1), Fe_2O_3, and Fe_3O_4, respectively, leading to modulation of Fe 3d-O 2p orbital hybridization and thus the K_(eff). On the other hand, we find that the introduction of Fe atoms also helps to reduce the multilayers' magnetic damping.