Edge-mediated skyrmion chain and its collective dynamics in a confined geometry.

Haifeng Du,Yuheng Zhang,Chao Wang,Wei Ning,Changqing Jin,Lingyao Kong,Renchao Che,Xianhui Chen,Jiadong Zang,Xuebing Zhao,Mingliang Tian,Jiyong Yang,Runwei Li,Chiming Jin

doi:10.1038/ncomms9504

Abstract

The emergence of a topologically nontrivial vortex-like magnetic structure, the magnetic skyrmion, has launched new concepts for memory devices. Extensive studies have theoretically demonstrated the ability to encode information bits by using a chain of skyrmions in one-dimensional nanostripes. Here, we report experimental observation of the skyrmion chain in FeGe nanostripes by using high-resolution Lorentz transmission electron microscopy. Under an applied magnetic field, we observe that the helical ground states with distorted edge spins evolve into individual skyrmions, which assemble in the form of a chain at low field and move collectively into the interior of the nanostripes at elevated fields. Such a skyrmion chain survives even when the width of the nanostripe is much larger than the size of single skyrmion. This discovery demonstrates a way of skyrmion formation through the edge effect, and might, in the long term, shed light on potential applications.

Highlights

The emergence of a topologically nontrivial vortex-like magnetic structure, the magnetic skyrmion, has launched new concepts for memory devices
Recent advances have enabled the fabrication of high-quality MnSi nanowires synthesized by chemical method, but the complex crystal structure in the nanowires, such as the parallelogram crosssection and twin boundaries, is a big challenge in obtaining the skyrmion chain under a magnetic field aligned perpendicular to the nanowire, individual skyrmion cluster states can be identified in the magnetic fields along the long axis of the nanowire[18,19]
We have demonstrated that the edge can be used to control skyrmion formation in confined geometries

Summary

Introduction

The emergence of a topologically nontrivial vortex-like magnetic structure, the magnetic skyrmion, has launched new concepts for memory devices. Under an applied magnetic field, we observe that the helical ground states with distorted edge spins evolve into individual skyrmions, which assemble in the form of a chain at low field and move collectively into the interior of the nanostripes at elevated fields. Such a skyrmion chain survives even when the width of the nanostripe is much larger than the size of single skyrmion. The real spin configurations around the edge are severely smeared out in such small-size samples[15,16,17] Another challenge is the difficulty in obtaining nanostructured helical magnets with the desired geometries. Further systematic investigation of the magnetization dynamics of nanostripes with various widths unveils an edgemediated mechanism to create skyrmions in confined geometries at low temperatures

Methods

Results

Conclusion