Mutual Synchronization of Spin-Torque Nano-Oscillators Via Oersted Magnetic Fields Created by Waveguides

Nanoscale oscillators based on the spin-transfer torque effect are attractive candidates for the hardware implementation of neural networks using an array of coupled oscillators. Here, we demonstrate that the mutual coupling through rf strip lines can be used for synchronizing two spin-torque nano-oscillators (STNOs). Using the current nanotechnology, it is feasible to design asymmetric coupling between two STNOs via this scheme, which would mimic many biological neural networks. A unique feature of our experiment is that we can characterize the synchronized state by varying the phase as well as the strength of the coupling, going into the nonlinear regime.