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MA: Fachverband Magnetismus

MA 37: Spin Torque and Spin Excitations I

MA 37.10: Vortrag

Donnerstag, 3. April 2014, 12:00–12:15, HSZ 401

Spin torque switching of an in-plane magnetized system in a thermally activated region — Tomohiro Taniguchi¹, Yasuhiro Utsumi², •Michael Marthaler³, Dmitri Golubev³, and Hiroshi Imamura¹ — ¹Spintronics Research Center, AIST, Tsukuba — ²Faculty of Engineering, Mie University, Tsu — ³Institut für Theoretische Festkörperphysik, KIT, Karlsruhe

The current dependence of the exponent of the spin torque switching rate of an in-plane magnetized system was investigated by solving the Fokker-Planck equation with low temperature and small damping and current approximations. We derived the analytical expressions of the critical currents, I_c and I_c^*. At I_c, the initial state parallel to the easy axis becomes unstable, while at I_c^* (≃ 1.27 I_c) the switching occurs without the thermal fluctuation. The current dependence of the exponent of the switching rate is well described by (1−I/I_c^*)^b, where the value of the exponent b is approximately unity for I < I_c, while b rapidly increases up to 2.2 with increasing current for I_c < I < I_c^*. The linear dependence for I < I_c agrees with the other works, while the nonlinear dependence for I_c < I < I_c^* was newly found by the present work. The nonlinear dependence is important for analysis of the experimental results, because most experiments are performed in the current region of I_c < I < I_c^*.