Dynamic transition of current-driven single-skyrmion motion in a room-temperature chiral-lattice magnet

Licong Peng,Yasujiro Taguchi,Yoshinori Tokura,Kosuke Karube,Naoto Nagaosa,Xiuzhen Yu

doi:10.1038/s41467-021-27073-2

Abstract

Driving and controlling single-skyrmion motion promises skyrmion-based spintronic applications. Recently progress has been made in moving skyrmionic bubbles in thin-film heterostructures and low-temperature chiral skyrmions in the FeGe helimagnet by electric current. Here, we report the motion tracking and control of a single skyrmion at room temperature in the chiral-lattice magnet Co9Zn9Mn2 using nanosecond current pulses. We have directly observed that the skyrmion Hall motion reverses its direction upon the reversal of skyrmion topological number using Lorentz transmission electron microscopy. Systematic measurements of the single-skyrmion trace as a function of electric current reveal a dynamic transition from the static pinned state to the linear flow motion via a creep event, in agreement with the theoretical prediction. We have clarified the role of skyrmion pinning and evaluated the intrinsic skyrmion Hall angle and the skyrmion velocity in the course of the dynamic transition. Our results pave a way to skyrmion applications in spintronic devices.

Highlights

Driving and controlling single-skyrmion motion promises skyrmion-based spintronic applications
The negative value of the applied magnetic field means that the field is directed along –zdirection, i.e., from the top to the bottom of the sample, which leads to the magnetizations pointing upwards at the skyrmion center and downwards at the periphery (Fig. 1d)
Under the pulsed current stimulation, the skyrmion exhibits a trapping-limited motion: it moves during the short current pulse and is trapped by nearby pinning sites after the stimulus, where the skyrmion can deform, as exemplified by Fig. 2c, d and Supplementary Fig. 4m

Summary

Introduction

Driving and controlling single-skyrmion motion promises skyrmion-based spintronic applications. Progress has been made in moving skyrmionic bubbles in thin-film heterostructures and low-temperature chiral skyrmions in the FeGe helimagnet by electric current. Systematic measurements of the single-skyrmion trace as a function of electric current reveal a dynamic transition from the static pinned state to the linear flow motion via a creep event, in agreement with the theoretical prediction. Skyrmions possess topological stability described by the integer character of their topological number Nsk,[3] This topological characteristic imparts skyrmions with particle-like properties, extraordinary metastability[4,5], and emergent electromagnetic phenomena[1–3]. The skyrmion motion exhibits a dynamic transition with increasing the driving current, i.e., from the static pinned state to the flow motion by way of a creep motion, as suggested by numerical simulations[11,12]. Driving skyrmionic bubbles requires a high current density of ~1010–1012 A m−2 to overcome the randomly distributed pinning sites in synthetic multilayered films prepared by magnetron sputtering techniques[13–17]

Methods

Results

Conclusion