A Coherent Spin-Torque Nano-oscillator Excited by a Combined Out-of-Plane and In-Plane Spin Polarized Current

We present a coherent spin-torque nano-oscillator (STNO) with spectral linewidths ≤ 10 MHz based on a nanopillar spin-valve device in which an in-plane magnetic free layer (FL) is excited by a combined out-of-plane and in-plane spin-polarized current under external magnetic fields, approximately cancelling the average in-plane dipolar field. The STNO exhibits enhanced nonlinear effective damping (Γ_eff) in the coherent region, resulting from the torque competition from the two spin polarizers and the spatial variation of the anti-damping effectiveness. This effectively reduces the nonlinear coupling (υ) between the amplitude and the phase fluctuations.