Nonlinear ferromagnetic resonance induced by spin torque in nanoscale magnetic tunnel junctions

Spin transfer torque can excite ferromagnetic resonance of magnetization in a nanoscale magnetic tunnel junction. Here we describe a strongly nonlinear regime of spin-torque-driven ferromagnetic resonance in which large-amplitude magnetization oscillations are excited by microwave current applied to the junction. In this nonlinear regime, the junction generates a large direct voltage in response to the applied microwave signal and thereby can serve as a sensitive microwave signal detector. We demonstrate a low-temperature detector sensitivity of 2.5 × 104 V/W, which exceeds the sensitivity of metal-semiconductor Schottky diodes.