Elongated Skyrmion as Spin Torque Nano-Oscillator and Magnonic Waveguide

TL;DR

This paper introduces a novel skyrmion-based spin torque nano-oscillator driven by uniform current, which uses elongated skyrmions for oscillation and can also function as a magnonic waveguide for logic devices.

Contribution

It presents a new mechanism for skyrmion oscillation via deformation of elongated skyrmions and demonstrates their dual role as oscillators and magnonic waveguides.

Findings

Oscillation frequency depends on current, damping, and pinning site properties.

Universal nonlinear response observed in skyrmions, antiskyrmions, skyrmioniums, and domain walls.

Elongated skyrmion waveguide enables spin wave propagation for logic applications.

Abstract

Spin torque nano-oscillator has been extensively studied both theoretically and experimentally in recent decades due to its potential applications in future microwave communication technology and neuromorphic computing. In this work, we present a skyrmion-based spin torque nano-oscillator driven by a spatially uniform direct current, where the skyrmion is confined by two pinning sites. Different from other skyrmion-based oscillators that arise from the circular motion or the breathing mode of a skyrmion, the steady-state oscillatory motions are produced by the periodic deformation of an elongated skyrmion. Through micromagnetic simulations, we find that the oscillation frequency depends on the driving current, the damping constant as well as the characteristics of pinning sites. This nonlinear response to direct current turns out to be universal and can also appear in the case of antiskyrmions, skyrmioniums and domain walls. Furthermore, the elongated skyrmion possesses a rectangle-like domain wall, which could also serve as a magnonic waveguide. Utilizing the propagation of spin waves in this waveguide, we propose a device design of logic gate and demonstrate its performance.