We have fabricated nanoscale magnetic tunnel junctions (MTJs) with an additional fixed magnetic layer added above the magnetic free layer of a standard MTJ structure. This acts as a second source of spin-polarized electrons that, depending on the relative alignment of the two fixed layers, either augments or diminishes the net spin-torque exerted on the free layer. The compound structure allows a quantitative comparison of spin-torque from tunneling electrons and from electrons passing through metallic spacer layers, as well as analysis of Joule selfheating effects. This has significance for current-switched magnetic random access memory (MRAM), where spin torque is exploited, and for magnetic sensing, where spin torque is detrimental.
@article{arxiv.cond-mat/0503376,
title = {Adjustable spin torque in magnetic tunnel junctions with two fixed layers},
author = {G. D. Fuchs and I. N. Krivorotov and P. M. Braganca and N. C. Emley and A. G. F. Garcia and D. C. Ralph and R. A. Buhrman},
journal= {arXiv preprint arXiv:cond-mat/0503376},
year = {2009}
}