Influence of inverse spin Hall effect in spin-torque ferromagnetic resonance measurements

We have performed spectral analyses of spin-torque ferromagnetic resonance (ST-FMR) signals in both Ni80Fe20/Ta and Co40Fe40B20/Ta bilayers and compared the spin Hall angles of these signals. We found that the contribution of the inverse spin Hall effect to the total signal in ST-FMR measurements is marked particularly in the case of Co40Fe40B20/Ta bilayers, because the anisotropic magnetoresistance effect in Co40Fe40B20, i.e., the origin of the ST-FMR signal, is much smaller than that in Ni80Fe20. When we take into account the contribution of the inverse spin Hall effect, the spin Hall angle of Co40Fe40B20/Ta decreases to less than half of that estimated by conventional ST-FMR spectral analysis. (C) 2016 The Japan Society of Applied Physics