Injection locking of the gyrotropic vortex motion in a nanopillar

Spin-torque oscillators (STOs) are a promising application for the spin-transfer torque effect. The major challenge lies in pushing the STO's microwave output power to useful levels, e. g., by operating an array of STOs in a synchronized, phase-locked mode. Our experiment on metallic, giant magnetoresistance-type nanopillars focuses on the influence of external high-frequency signals on the current-driven vortex dynamics and demonstrates the injection locking of the gyrotropic mode. We find a gap of about three orders of magnitude between the high-frequency power emitted by one oscillator and the power needed for phase-locking. (C) 2010 American Institute of Physics. [doi:10.1063/1.3498009