Spin transfer effects in current perpendicular to the plane spin valves

We present experimental and numerical micromagnetic data that illustrate manifestations of spin momentum transfer in current perpendicular to the plane spin valves. Noise measurements confirm predictions of current induced magnetization dynamics due to spin torque, where the dynamics are observable only for those combinations of current direction and magnetic configuration in which spin transfer acts to reorient the free layer magnetization away from the direction set by the net magnetic field. The evolution of the amplitude and spectral characteristics of the noise with varying current and magnetic configuration are also discussed.