Parametric oscillator based on non-linear vortex dynamics in low resistance magnetic tunnel junctions

TL;DR

This paper investigates low-resistance magnetic tunnel junctions as radiofrequency vortex spin-transfer oscillators, demonstrating high power excitations, harmonic generation, and efficient synchronization via parametric resonance.

Contribution

It introduces a parametric oscillator model based on non-linear vortex dynamics in low-resistance magnetic tunnel junctions, highlighting synchronization phenomena.

Findings

High power spectral density with sharp fundamental and harmonic peaks

Synchronization is most effective when external frequency is twice the fundamental

Behavior explained by combined effects of spin transfer torque and Oersted-Ampère field

Abstract

Radiofrequency vortex spin-transfer oscillators based on magnetic tunnel junctions with very low resistance area product were investigated. A high power of excitations has been obtained characterized by a power spectral density containing a very sharp peak at the fundamental frequency and a series of harmonics. The observed behaviour is ascribed to the combined effect of spin transfer torque and Oersted-Amp\`ere field generated by the large applied dc-current. We furthermore show that the synchronization of a vortex oscillation by applying a ac bias current is mostly efficient when the external frequency is twice the oscillator fundamental frequency. This result is interpreted in terms of a parametric oscillator.