Spin torque

Spin-Torque Switching with the Giant Spin Hall Effect of Tantalum.
Luqiao Liu, Chi-Feng Pai, Y. Li, H. W. Tseng, D. C. Ralph, R. A. Buhrman
Science 336, 555 (2012)

ST-FMR induced by the spin Hall effect at room temperature. (A) Sample geometry for the ST-FMR measurement. IRF and HRF represent the applied radio frequency current and the corresponding Oersted field. Tau_h is the torque on the magnetization due to the Oersted field, and Tau_ST is the spin-transfer torque from the spin Hall effect. Resonant line shapes of the STFMR signals under a driving frequency f = 9 GHz for (B) CoFeB(4 nm)/Ta(8 nm) and (C) CoFeB(3 nm)/Pt
(6 nm). The squares represent experimental data, whereas the red curves are fits to a sum of symmetric and antisymmetric Lorentzians. From the ratio of the symmetric and antisymmeteric peak components in (C), we determine the JS/Je ratio for Pt to be ~0.07, consistent with earlier work (19). Vmix is the measured dc voltage due to the mixing of oscillating resistance and radio frequency current. The inset to (B) shows the dependence of the frequency f on the resonance magnetic field, in agreement with the Kittel formula (solid curve). (D) The resonance linewidth as determined from ST-FMR signals such as
those shown in (B) and (C) at different resonance frequencies. The Gilbert damping coefficients a for Ta and Pt are calculated from the linear fits to these linewidth data. CFB, CoFeB.