Time required to injection-lock spin torque nanoscale oscillators

We have injection-locked a spin-transfer oscillator to a second-harmonic electrical input signal and measured the relative phase and amplitude of the device output as a function of DC current under steady-state conditions. The relative phase of the device varies quasi-linearly with DC bias, although the averaged amplitude decreases significantly outside of the spectrally determined locking range. By pulsing the injected microwaves, the time required for the device to phase-lock to the injected signal was measured as a function of microwave amplitude. The locking time varied quasi-linearly over the range of amplitudes studied, with the shortest locking times being a few nanoseconds.