We predict an anomalous bias dependence of the spin transfer torque parallel to interface, T∣∣, in magnetic tunnel junctions (MTJ), which can be selectively tuned by the exchange splitting. It may exhibit a sign reversal {\it without} a corresponding sign reversal of the bias or even a quadratic bias dependence. We demonstrate that the underlying mechanism is the interplay of spin currents for the ferromagnetic (antiferromagnetic) configurations, which vary linearly (quadratically) with bias, respectively, due to the symmetric (asymmetric) nature of the barrier. The spin transfer torque perpendicular to interface exhibits a quadratic bias dependence.
@article{arxiv.cond-mat/0606080,
title = {Anomalous Bias Dependence of Spin Torque in Magnetic Tunnel Junctions},
author = {Ioannis Theodonis and Nicholas Kioussis and Alan Kalitsov and Mairbek Chshiev and William Butler},
journal= {arXiv preprint arXiv:cond-mat/0606080},
year = {2007}
}