Nanowire Spin-Torque Oscillator With Non-Uniform Polarizer: A Micromagnetic Study

This paper studies the dynamical response of a magnetic nanowire driven by a localized spin-polarized current. At zero field and with shifted vortex polarizer, the dispersion relation is characterized by a finite wave vector at microwave frequencies approaching the ferromagnetic resonance frequency. We have interpreted this result by assuming that a given mixed mode of the nanowire having a frequency close to the quasi-uniform mode is excited because of the non-uniform current polarization. For out-of-plane fields, we have observed that, for a fixed frequency, the wave vector of a propagating spin-wave does not depend on whether the excitation was performed by means of either dc or microwave current.