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Spin-Transfer Switching of Perpendicularly Magnetized Spin-valve Devices

Spin-Transfer Switching of Perpendicularly Magnetized Spin-valve Devices H. Liu 1* , D. Bedau 1 , J-J. Bouzaglou 1,3 , A. D. Kent 1 , J. Z. Sun 2 , J. A. Katine 4 , E. E. Fullerton 5 and S. Mangin 3 * : Presenter

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Spin-Transfer Switching of Perpendicularly Magnetized Spin-valve Devices

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  1. Spin-Transfer Switching of Perpendicularly Magnetized Spin-valve Devices H. Liu1*, D. Bedau1, J-J. Bouzaglou1,3, A. D. Kent1, J. Z. Sun2, J. A. Katine4, E. E. Fullerton5 and S. Mangin3 * : Presenter 1Department of Physics, New York University, New York, NY 10003, USA 2IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York, 10598, USA 3LPM, Nancy-Université, UMR CNRS 7556, F-54506 VandoeuvreCedex, France 4San Jose Research Center, Hitachi-GST, San Jose, California 95135, USA 5CMRR, University of California, San Diego, La Jolla, California 92093-0401, USA e mp electron m magnetization MOTIVATION EXPERIMENTAL TECHNIQUES DATA AND ANALYSIS DATA AND ANALYSIS THEORETICAL MODELLING • If we consider no thermal effects in the switching process, the switching probability distribution (between no switch and all switch) can only be the results of thermal fluctuation in the initial and final condition. Here, we assume the initial state of our sample is in thermal equilibrium and obeys Boltzmann distribution. Then we fit the experimental data using the full solution from the LLG equation with this assumption: • Spin torque – the amount of transverse angular momentum transferred in unit time. • Landau-Lifshitz-Gilbert (LLG) equation + Spin Torque: • where • For all-perpendicular magnetization configuration: • And if we assume that thermal fluctuation will NOT influence the process of switching if the duration of switching is short enough, then we have: • And : • where: is the final (initial) angle of the switching, and • This equation can be linearized as[1],[2]: • where A is the dynamic parameter, and Ic0 is the zero temperature critical current CONCLUSIONS We have demonstrated ultrafast switching for all-perpendicular spin valve with high efficiency by studying the dynamical regime, where the pulse duration is comparable to the precession time. The amplitude needed for switching is proportion to 1 / τ, as predicted by the macro spin model. We also find a linear dependence of the critical current and dynamic parameter on the applied easy-axis field as expected for the case of uniaxial anisotropy. Even though the switching process follows the predicted scaling law, the macro spin model does not account for all material parameters. REFERENCES J. Z. Sun, Proceedings of SPIE vol.5359, 445 (2004) J. Z. Sun, Physics Review B Volume 62, Number 1 (2000)

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