Spin transfer induced coherent microwave emission with large power from nanoscale MgO tunnel junctions

In low resistance-area product MgO magnetic tunnel junction nanopillars, we observe high integrated power (up to 43 nW), narrow linewidth (down to 10 MHz), spin transfer induced microwave emission at frequencies up to 14 GHz due to precession of the free layer magnetization at room temperature. Although all devices were fabricated on the same wafer, they present bimodal transport and precessional characteristics. The devices in which the narrowest linewidths were observed exhibited low resistance and tunneling magnetoresistance (30%), while maintaining large integrated power.