Author: ["Hitoshi Kubota","Akio Fukushima","Kay Yakushiji","Taro Nagahama","Shinji Yuasa","Koji Ando","Hiroki Maehara","Yoshinori Nagamine","Koji Tsunekawa","David D. Djayaprawira","Naoki Watanabe","Yoshishige Suzuki"]
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Abstract
When an electric current passes from one ferromagnetic layer via a non-magnetic layer into another ferromagnetic layer, the spin polarization and subsequent rotation of this current can induce a transfer of angular momentum that exerts a torque on the second ferromagnetic layer1,2,3,4. This provides a potentially useful method to reverse3,5,6,7 and oscillate8 the magnetic momenta in nanoscale magnetic structures. Owing to the large current densities required to observe spin-torque-induced magnetization switching and microwave emission (∼107 A cm−2), accurately measuring the strength, or even the direction, of the associated spin torque has proved difficult. Yet, such measurements are crucial to refining our understanding of the mechanisms responsible and the theories that describe them9,10. To address this, we present quantitative experimental measurements of the spin torque in MgO-based magnetic tunnel junctions11,12,13,14 for a wide range of bias currents covering the switching currents. The results verify the occurrence of two different spin-torque regimes with different bias dependences that agree well with theoretical predictions10.Cite this article
Kubota, H., Fukushima, A., Yakushiji, K. et al. Quantitative measurement of voltage dependence of spin-transfer torque in MgO-based magnetic tunnel junctions. Nature Phys 4, 37–41 (2008). https://doi.org/10.1038/nphys784 