Title :
Nanowire Spin-Torque Oscillator With Non-Uniform Polarizer: A Micromagnetic Study
Author :
Giordano, A. ; Carpentieri, Michele ; Zivieri, Roberto ; Siracusano, Giulio ; Azzerboni, Bruno ; Finocchio, Giovanni
Author_Institution :
Dept. of Electron. EngineeringIndustrial Chem. & Eng., Univ. of Messina, Messina, Italy
Abstract :
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.
Keywords :
Permalloy; cobalt alloys; copper; dispersion relations; electromagnetic wave polarisation; ferromagnetic resonance; magnetoelectronics; micromagnetics; nanomagnetics; nanowires; oscillators; spin polarised transport; Ni80Fe20-Cu-CoFe; dc current; dispersion relation; dynamical response; ferromagnetic resonance frequency; finite wave vector; magnetic nanowire; micromagnetic study; microwave current; nanowire spin-torque oscillator; nonuniform current polarization; nonuniform polarizer; out-of-plane fields; quasiuniform mode; shifted vortex polarizer; spin-polarized current; spin-wave propagation; Magnetic hysteresis; Magnetic resonance; Magnetization; Microwave oscillators; Saturation magnetization; Vectors; Ferromagnetic resonance (FMR) frequency; spin-wave excitation; vortex-state;
Journal_Title :
Magnetics, IEEE Transactions on
DOI :
10.1109/TMAG.2014.2330765