Berlin 2008 – scientific programme
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MA: Fachverband Magnetismus
MA 32: Postersession II: Spinstruct./Phase Trans. (1-10); Spinelectronics (11-15); Thin Films (16 - 36); Particles/Clusters (37-45); Multiferroics (46-54); Spindynamics/Spin Torque (55 - 76); Post Deadlines (77-79)
MA 32.67: Poster
Friday, February 29, 2008, 11:15–14:00, Poster E
Bias dependence of the spin transfer torque in Fe/MgO/Fe — •Christian Heiliger1,2, Paul M. Haney1, and Mark D. Stiles1 — 1Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899-6202 — 2Maryland NanoCenter, University of Maryland, College Park, MD, 20742
Recent experiments [1,2] have reached contradictory conclusions regarding the out-of-plane component of the spin transfer torque in Fe/MgO/Fe tunnel junctions. We use ab initio calculations as well as model calculations to investigate the bias dependence of the spin transfer torque in tunnel junctions. We use the non-equilibrium Keldysh formalism implemented in a Korringa-Kohn-Rostoker method to calculate the spin transfer torque [3]. We find that under certain circumstances one can estimate the bias dependence of the spin transfer torque at small biases in terms of the non-equilibrium torques at the Fermi level for zero bias. In ideal Fe/MgO/Fe junctions we find a small linear dependence of the out-of-plane torque on voltage. However, this torque oscillates rapidly with layer thicknesses and should cancel in samples with realistic roughness. This work has been supported in part by the NIST-CNST/UMD-NanoCenter Cooperative Agreement.
[1] A. A. Tulapurkar et al., Nature 438, 339 (2005).
[2] J. C. Sankey et al., Phys. Rev. Lett. 96, 227601 (2006).
[3] C. Heiliger et al., J. Appl. Phys. (in press); arXiv:0711.2082.