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.

Stable skyrmions in Co/Ni-based nanopillars with perpendicular magnetization anisotropy

“…Skyrmion-based memory devices have gained significant attention due to their numerous advantages, such as ultrahigh density, low power consumption, high stability, and high speed [1][2][3][4][5][6][7][8]. Therefore, there has been a growing interest in exploring new materials, physical properties, and prototype devices related to skyrmions, making it a cross research hotspot [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. With the advancements in device processing and control technology, various methods of stimulating and producing skyrmions have diversified, including spin current [27,28], spin Hall effect [29], temperature * Authors to whom any correspondence should be addressed.…”

Asymmetric Magnon Frequency Comb

“…The physical model we consider is depicted in Figure a, consisting of a single magnetic skyrmion coupled to two nearby magnon waveguides (labeled as WG1 and WG2, respectively). Because the magnetization inside a skyrmion rotates smoothly from downward at the core to upward at the perimeter, the skyrmion can be regarded as a circular 180° domain wall that naturally serves as a nanocavity and supports the magnonic WGM. ,, When the driving SW mode is incident from the left port of WG1, a clockwise (CW) mode of the same frequency inside the skyrmion is excited and then chirally coupled to WG2. The transmission path of the driving SW is denoted by the red arrows shown in Figure a, and the phase matching diagram at the coupling region between the skyrmion and WG2 is illustrated in Figure b.…”