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

Abstract

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 (Gamma(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 (upsilon) between the amplitude and the phase fluctuations.