Spin-Torque-Induced Rotational Dynamics of a Magnetic Vortex Dipole
  We study, both experimentally and by numerical modeling, the magnetic dynamics that can be excited in a magnetic thin-film nanopillar device using the spin torque from a spatially localized current injected via a 10s-of-nm-diameter aperture. The current-driven magnetic dynamics can produce large amplitude microwave emission at zero magnetic field, with a frequency well below that of the uniform ferromagnetic resonance mode. Micromagnetic simulations indicate that the physical origin of this efficient microwave nano-oscillator is the nucleation and subsequent steady-state rotational dynamics of a magnetic vortex dipole driven by the localized spin torque. These results show this novel implementation of a spintronic nano-oscillator is a promising candidate for microwave technology applications. 
G. Finocchio, O. Ozatay, L. Torres, R. A. Buhrman, D.C. Ralph, B.   Azzerboni