Spin-torque magnetic nano-structures as microwave sources

In experimental microwave sources based on spin-torque magnetic nano-structures (MNS) the power is extracted as oscillation of the device magnetoresistance (MR). The goal of our work is to evaluate the magnitude of the microwave power that can be extracted from a MNS through the oscillating dipolar fields when the MNS is coupled to different microwave systems, and to compare this power with the power that can be extracted through the traditional MR mechanism. We demonstrate that, although for a single MNS the MR mechanism is much more efficient than the direct dipolar electromagnetic emission, the latter mechanism can have a significant advantage in the case of a sufficiently large array of synchronized MNS placed in a microwave resonator.