Elongated skyrmion as spin torque nano-oscillator and magnonic waveguide

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 an elongated 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 motion is produced by the periodic deformation of the elongated skyrmion, which originates from the oscillation of its partial domain walls under the joint action of spin torques, the damping and the boundary effect. Micromagnetic simulations are performed to demonstrate the dependence of the oscillation frequency on the driving current, the damping constant, the magnetic parameters as well as the characteristics of pinning sites. This nonlinear response to a direct current turns out to be universal and can also appear in the case of elongated antiskyrmions, skyrmioniums and domain walls. Furthermore, the elongated skyrmion possesses a rectangle-like domain wall, which could also serve as a magnonic waveguide. These findings will enrich the design options for future skyrmion-based devices in the information technology.