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Large-amplitude coherent spin waves exited by spin-polarized current in nanoscale spin valves

I. N. Krivorotov·D. V. Berkov·N. L. Gorn·N. C. Emley·J. C. Sankey·D. C. Ralph·R. A. Buhrman
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Abstract

We present spectral measurements of spin-wave excitations driven by direct spinpolarized current in the free layer of nanoscale Ir20Mn80/Ni80Fe20/Cu/Ni80Fe20 spin valves. The measurements reveal that large-amplitude coherent spin wave modes are excited over a wide range of bias current. The frequency of these excitations exhibits a series of jumps as a function of current due to transitions between different localized nonlinear spin wave modes of the Ni80Fe20 nanomagnet. We find that micromagnetic simulations employing the Landau-Lifshitz-Gilbert equation of motion augmented by the Slonczewski spin torque term (LLGS) accurately describe the frequency of the current-driven excitations including the mode transition behavior. However LLGS simulations give qualitatively incorrect predictions for the amplitude of excited spin waves as a function of current.

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I. N. Krivorotov, D. V. Berkov, N. L. Gorn, N. C. Emley, J. C. Sankey, D. C. Ralph, R. A. Buhrman. 2007-03-22. Large-amplitude coherent spin waves exited by spin-polarized current in nanoscale spin valves. https://doi.org/10.1103/physrevb.76.024418

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