Ultrahigh Frequency and Multichannel Output Skyrmion-Based Nano-Oscillator

Abstract

Spintronic-based skyrmion nano-oscillators can generate tunable microwave signals that find a wide range of applications in the field of telecommunication to modern neuromorphic computing systems. Skyrmions within a single ferromagnet (FM) material encounter an undesired Magnus force, which imposes limitations on the oscillator’s frequency, typically reaching only a few gigahertz. However, for applications requiring higher data transmission speeds, oscillator frequencies must be elevated to tens of GHz. Conversely, a bilayer device featuring two FM layers coupled in a synthetic anti-ferromagnetic (SAF) configuration can effectively neutralize the Magnus force. Utilizing the bilayer device concept, we propose a multichannel oscillator design, and using micromagnetic simulations, we demonstrate that our proposed device could achieve an ultrahigh frequency of 41 GHz. The ultrahigh operational frequency represents a $\sim 342\times $ improvement compared to the monolayer single skyrmion oscillator. We demonstrate the effectiveness of our proposed multichannel oscillator design by introducing multichannel nanotracks along with multiple skyrmions for enhanced frequency operation. The ultrahigh operational frequency and multichannel output are attributed to three key factors: 1) higher spin-flip length of the spacer (such as Ru) material, separating two FM layers; 2) tangential velocity, proportionality on input spin current along with weak dependence on the radius of rotation of the skyrmion-pair; and 3) skyrmion interlocking in the channel enabled by the multichannel high anisotropy rings and skyrmion-skyrmion repulsion.