Coupled spin torque nano-oscillators: Stability of synchronization

Abstract

In this work we explore the use of spin torque nano-oscillators (STNOs) to produce a spintronics voltage oscillator in the microwave range. STNOs are quite small—on the order of 100 nm—and frequency agile. However, experimental results till date have produced power outputs that are too small for practical use. We attempt to increase power output by investigating the dynamics of a system of electrically coupled STNOs. Transverse Lyapunov exponents are used to quantitatively measure the local stability of synchronized limit cycles. The synchronized solution is found to be stable for a large region of two-parameter space. However, a two-parameter bifurcation diagram reveals a competing out-of-phase solution, causing bistability.