Time domain detection of pulsed spin torque damping reduction

Combining multiple ultrafast spin torque impulses with a 5 nanosecond duration pulse for damping reduction, we observe time-domain precession which evolves from an initial 1 ns duration transient with changing precessional amplitude to constant amplitude oscillations persisting for over 2 ns. These results are consistent with relaxation of the transient trajectories to a stable orbit with nearly zero damping. We find that in order to observe complete damping cancellation and the transient behavior in a time domain sampling measurement, a short duration, fast rise-time pulse is required to cancel damping without significant trajectory dephasing.