Synchronization of spin-torque driven nanooscillators for point contacts on a quasi-1D nanowire: Micromagnetic simulations

TL;DR

This study uses micromagnetic simulations to explore long-distance synchronization of spin-torque nanooscillators on a quasi-1D nanowire, revealing new behaviors and conditions affecting stable synchronization.

Contribution

It demonstrates the possibility of long-distance synchronization of STNOs in a quasi-1D geometry and uncovers new features influencing synchronization stability.

Findings

Synchronization possible up to 3 micrometers distance

Existence of a minimal contact distance for synchronization

Multiple synchronized states can occur at same current values

Abstract

In this paper we present detailed numerical simulation studies on the synchronization of two spin-torque nanooscillators (STNO) in the quasi-1D geometry: magnetization oscillations are induced in a thin NiFe nanostripe by a spin polarized current injected via square-shaped CoFe nanomagnets on the top of this stripe. In a sufficiently large out-of-plane field, a propagating oscillation mode appears in such a system. Due to the absence of the geometrically caused wave decay in 1D systems, this mode is expected to enable a long-distance synchronization between STNOs. Indeed, our simulations predict that synchronization of two STNOs on a nanowire is possible up to the intercontact distance 3 mkm (for the nanowire width 50 nm). However, we have also found several qualitatively new features of the synchronization behaviour for this system, which make the achievement of a stable synchronization in this geometry to a highly non-trivial task. In particular, there exist a minimal distance between the nanocontacts, below which a synchronization of STNOs can not be achieved. Further, when the current value in the first contact is kept constant, the amplitude of synchronized oscillations depends non-monotonously on the current value in the second contact. Finally, for one and the same currents values through the contacts there might exist several synchronized states (with different frequencies), depending on the initial conditions.