Quasilinear spin-torque nano-oscillator via enhanced negative feedback of power fluctuations

We report on an approach to improving the performance of spin-torque nano-oscillators (STNOs) that utilizes power-dependent negative feedback to achieve significantly enhanced dynamic damping. In combination with a sufficiently slow variation of frequency with power, this can result in a quasilinear STNO, with weak nonlinear coupling of power and phase fluctuations over a range of bias currents and fields. An implementation of this approach that utilizes nonuniform spin torque applied to the oscillating magnetic free layer of a nanoscale spin-valve device demonstrates that highly coherent room-temperature STNOs can be achieved while retaining sufficient tunability.