Transfer of angular momentum from a spin-polarized current to a ferromagnet provides an efficient means to control the dynamics of nanomagnets. A peculiar consequence of this spin-torque, the ability to induce persistent oscillations of a nanomagnet by applying a dc current, has previously been reported only for spatially uniform nanomagnets. Here we demonstrate that a quintessentially nonuniform magnetic structure, a magnetic vortex, isolated within a nanoscale spin valve structure, can be excited into persistent microwave-frequency oscillations by a spin-polarized dc current. Comparison to micromagnetic simulations leads to identification of the oscillations with a precession of the vortex core. The oscillations, which can be obtained in essentially zero magnetic field, exhibit linewidths that can be narrower than 300 kHz, making these highly compact spin-torque vortex oscillator devices potential candidates for microwave signal-processing applications, and a powerful new tool for fundamental studies of vortex dynamics in magnetic nanostructures.
@article{arxiv.cond-mat/0702253,
title = {Magnetic vortex oscillator driven by dc spin-polarized current},
author = {V. S. Pribiag and I. N. Krivorotov and G. D. Fuchs and P. M. Braganca and O. Ozatay and J. C. Sankey and D. C. Ralph and R. A. Buhrman},
journal= {arXiv preprint arXiv:cond-mat/0702253},
year = {2015}
}