Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 22: Spin Dynamics / Spin Torque III
MA 22.3: Vortrag
Donnerstag, 25. März 2010, 10:15–10:30, H10
Optimum tunnel barrier thickness for spin torque memory devices — •Santiago Serrano-Guisan1, W. Skowronski2, N. Liebling1, J. Wrona2, M. Czapkiewicz2, T. Stobiecki2, J. Langer3, B. Ocker3, G. Reiss4, and H.W. Schumacher1 — 1Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116, Braunschweig, Germany — 2AGH University of Science and Technology, Department of Electronics, Al. Mickiewicza 30, 30059 Krakow, Poland — 3Singulus, Hanauer Landstrasse 103, 63796 Kahl am Main, Germany — 4Bielefeld University, Department of Physics, P.O. Box 100131, 33501 Bielefeld, Germany
We study the influence of the exchange coupling strength JFP between the free and the reference layer magnetization on the precessional magnetization dynamics in CoFeB/MgO/CoFeB based magnetic tunnelling junction stacks with different MgO barrier thickness (tMgO) by pulse inductive microwave magnetometry (PIMM). From PIMM data the field dependent precession frequency f and the effective Gilbert damping α as well as their respective dependence on tMgO are derived. For tMgO < 0.76 nm the strong JFP inhibits reversal of the free layer. However, for a thickness range 0.85 nm > tMgO > 0.76 nm free layer reversal is possible and a relative low damping α ≈ 0.017 ± 0.003 is found with no significant barrier thickness dependence. For such relatively low α, a low current density spin torque reversal is expected as it scales linearly with α. Additionally, the large TMR ratios (larger than 150%) and small RA products (2-4 Ωµm2) occurring in this thickness range make it optimum for ST memory applications