High frequency spin-torque-oscillators with reduced perpendicular torque effect based on asymmetric vortex polarizer

In this paper it is demonstrated micromagnetically the possibility to have high frequency and high power microwave emission at zero field in magnetic tunnel junctions with an off-centered vortex polarizer for current densities smaller than 107 A/cm2. We found power spectra characterized by two harmonics (around 6 GHz and 12 GHz) where the second one has the larger power. Due to the non-uniform configuration of the polarizer, the effect of the perpendicular torque is partially compensated by the Oersted field. Our predictions give rise to the design of a more compact and easily embedded spin-torque oscillators for all-on-chip applications.