Current-driven microwave oscillations in current perpendicular-to-plane spin-valve nanopillars

摘要

We study the current and temperature dependences of the microwave voltage emission of spin-valve nanopillars subjected to an in-plane magnetic field and a perpendicular-to-plane current. Despite the complex multilayer geometry, clear microwave emission is observed for current densities in the interval of 9 X 10~7 - 13 X 10~7 A cm~(-2). The emission frequency stays near 12 GHz when I < I_(red) = 11.2 X 10~7 A cm~(-2), then redshifts with a slope gradually reaching -350 MHz/mA for 16 X 10~7 A cm~(-2). The linewidth narrows exponentially to 3.8 MHz at 150 K for I < I_(red), then broadens again as the emitted voltage redshifts. The temperature dependence of the linewidth exhibits a curvature change around the linewidth minimum.