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.
@article{arxiv.cond-mat/0703458,
title = {Large-amplitude coherent spin waves exited by spin-polarized current in nanoscale spin valves},
author = {I. N. Krivorotov and D. V. Berkov and N. L. Gorn and N. C. Emley and J. C. Sankey and D. C. Ralph and R. A. Buhrman},
journal= {arXiv preprint arXiv:cond-mat/0703458},
year = {2009}
}
Comments
24 pages, 4 figures, submitted to Physical Review B; in the 1st revised version some references were corrected