Motion of a skyrmionium driven by spin wave

Abstract

A skyrmionium is composed of two skyrmions with opposite skyrmion numbers and different sizes in the same track. In recent years, the motion of a skyrmionium driven by spin-polarized current has been investigated. However, the motion of a skyrmionium driven by a spin wave has not been reported. In this paper, we report our work concerning the numerical analysis of spin wave-driven motion of a skyrmionium in a nanotrack. The results show that the motion of a skyrmionium was significantly influenced by varying the frequency and amplitude of the AC magnetic field for exciting a spin wave, the distance between the spin wave source and the skyrmionium, the damping coefficient of the ferromagnetic track, and the track width. We found skyrmionium deformation during its initial motion process, but its shape could be recovered as it moved farther away from the spin wave source. Additionally, a series of velocity peaks were observed in the frequency range between 25 GHz and 175 GHz. When compared to a skyrmion, the skyrmionium could be driven by a spin wave to move in a wider frequency range at a higher velocity, and the velocity of the skyrmionium kept increasing with the increase in the track width till the track edge was far away from the skyrmionium. The result offers skyrmionium potential applications in wide-frequency spintronic devices.

Skyrmionium – high velocity without the skyrmion Hall effect

“…Skyrmionium can be moved inside a nanotrack by spin waves 61 , 62 , magnetic field gradient 31 , 33 and spin-polarized current 32 , 34 , 63 . In this section, we demonstrate the spin current-dependent dynamics of a skyrmionium in comparison with a skyrmion and analyze the skyrmionium stability under the current action.…”

Magnetic skyrmionium diode with a magnetic anisotropy voltage gating

“…On the other hand, a magnetic skyrmionium is also a topological spin texture with Q ¼ 0. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] It has a doughnut-like out-of-plane spin structure and can be seen as the combination of two skyrmions with opposite Q. The magnetic skyrmionium can be generated by ultra-fast laser pulses and has been observed experimentally 38 to be stable for over 12 months.…”

Electrical writing, deleting, reading, and moving of magnetic skyrmioniums in a racetrack device

“…Here, we utilize another type of magnetic quasi-particle ( Fig. 1a) with a zero topological charge: the skyrmionium (also called a 2π-skyrmion) [24][25][26][27][28][29][30][31][32][33][34] . The skyrmionium has been observed experimentally created by laser pulses 27 , as target skyrmionium in nanodiscs 28 and very recently in a thin ferromagnetic film on top of a topological insulator 29 .…”