Collective Behavior of an Array of Spin Torque Nano-Oscillators

P.L. Buono, C. Dabrowski, A. Palacios, J. Turtle, V. In
San Diego State University, US

Keywords: nano-valves, nano-oscillators, synchronization, microwave signals

Summary:

As predicted by Slonczewski and Berger, a spin-polarized current can exert a torque on the magnetization of a ferromagnetic layer leading to precession. Then the Giant Magnetoresistance Effect (GMR) can convert the magnetic precession into microwave voltage signals and turn the valve into a Spin Torque Nano-Oscillator (STNO) whose power output, about 1 nW, is small. To generate a more powerful signal, several groups have proposed to harness the power of several STNOs connected together, see but their collective behavior, which belongs to the field of nonlinear dynamics, has never been fully studied. In this work, we present a quantitative and qualitative analysis of the collective behavior of an array of STNOs connected in series. In particular, we study the nature of the bifurcations that lead the array to produce a collective pattern of synchronization and its potential to generate a large enough microwave signal at the nano-scale.