The spin-torque in magnetic tunnel junctions possesses two components that both depend on the applied voltage. Here, we develop a new method for the accurate extraction of this bias-dependence from experiments over large voltage ranges. We study several junctions with different magnetic layer structures of the top electrode. Our results obtained on junctions with symmetric CoFeB electrodes agree well with theoretical calculations. The bias-dependences of asymmetric samples, with top electrodes containing NiFe, however, are twisted compared to the quadratic form generally assumed. Our measurements reveal the complexity of spin-torque mechanisms at large bias.
@article{arxiv.1604.04517,
title = {Twist in the bias-dependence of spin-torques in magnetic tunnel junctions},
author = {Sören Boyn and João Sampaio and Vincent Cros and Julie Grollier and Akio Fukushima and Hitoshi Kubota and Kay Yakushiji and Shinji Yuasa},
journal= {arXiv preprint arXiv:1604.04517},
year = {2016}
}