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arXiv · 1705.02579

Enhancing the spin transfer torque in magnetic tunnel junctions by ac modulation

Xiaobin Chen·Chenyi Zhou·Zhaohui Zhang·Jingzhe Chen·Xiaohong Zheng·Lei Zhang·Can-Ming Hu·Hong Guo
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Abstract

The phenomenon of spin transfer torque (STT) has attracted a great deal of interests due to its promising prospects in practical spintronic devices. In this paper, we report a theoretical investigation of STT in a noncollinear magnetic tunnel junction under ac modulation based on the nonequilibrium Green's function formalism, and derive a closed-formulation for predicting the time-averaged STT. Using this formulation, the ac STT of a carbon-nanotube-based magnetic tunnel junction is analyzed. Under ac modulation, the low-bias linear (quadratic) dependence of the in-plane (out-of-plane) torque on bias still holds, and the $\sinθ$ dependence on the noncollinear angle is maintained. By photon-assisted tunneling, the bias-induced components of the in-plane and out-of-plane torques can be enhanced significantly, about 12 and 75 times, respectively. Our analysis reveals the condition for achieving optimized STT enhancement and suggests that ac modulation is a very effective way for electrical manipulation of STT.

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Xiaobin Chen, Chenyi Zhou, Zhaohui Zhang, Jingzhe Chen, Xiaohong Zheng, Lei Zhang, Can-Ming Hu, Hong Guo. 2017-05-07. Enhancing the spin transfer torque in magnetic tunnel junctions by ac modulation. https://doi.org/10.1103/physrevb.95.115417

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