Magnetization Switching by Spin–Orbit Torque in L10-FePt and Ta/FePt Films With Large Perpendicular Magnetic Anisotropy

Abstract

The current induced perpendicular magnetization switching in L10-FePt single layer and Ta/FePt bilayer thin films was investigated. Here, L10-FePt (6 nm) single-layer film and Ta (1-5 nm)/FePt (6 nm) bilayer films were deposited on MgO substrate at 700°C, showing good perpendicular anisotropy with the out-of-plane coercivity of 7.5 kOe for FePt and around 5 kOe for Ta/FePt bilayers. It is found that current-induced partial magnetization-based switching was realized with the SOT switching ratio of about 3% in all films. For adding the Ta capping layer, the critical current density is reduced and the stability of the switching loop is relatively better as compared with the single FePt layer. Furthermore, harmonic Hall voltage results demonstrate that the SOT efficiency (βDL) of FePt single-layer is approximately 50 Oe/ (107A cm-2), significantly higher than that of Ta/FePt bilayers, which is several times higher than that of the traditional Ta/CoFeB/MgO structure reported before. More importantly, Ta/FePt bilayer structure exhibits very good memristive switching behavior, which is expected to be applied to the spin-synapse of neural networks in the future.