Spin-Torque Nano-Oscillator as a Microwave Signal Source

We evaluate a possibility to use spin-torque nano-oscillators (STNOs) and oscillator arrays as new sources of microwave signals for telecommunication devices. The microwave signal generated by STNO can be received as oscillation of the device magnetoresistance (MR) or as direct electromagnetic emission of two effective magnetic dipoles. We calculate the dipolar microwave power emitted by STNO in free space and in several types of transmission lines and resonators. We demonstrate that although the power of a single STNO received through the MR effect is, typically, larger than the power of direct microwave emission of effective dipoles, the latter mechanism might have an advantage for sufficiently large arrays of coupled STNOs.