Effects of radio-frequency current on spin-transfer-torque-induced dynamics

The impact of radio-frequency (rf) currents on the direct current (dc)-driven switching dynamics in current-perpendicular-to-plane nanoscale spin valves is demonstrated. The rf currents can dramatically alter the dc-driven free layer magnetization reversal dynamics as well as the dc switching level. The effects occur when the frequency of the rf current is tuned to a frequency range around the dc-driven magnetization precession frequencies. For these frequencies, interactions between the dc-driven precession and the injected rf induce frequency locking and frequency pulling effects that lead to a measurable dependence of the critical switching current on the frequency of the injected rf. Based on macrospin simulations, including dc as well as rf spin torque currents, we explain the origin of the observed effects.