Skyrmion production on demand by homogeneous DC currents

Karin Everschor-Sitte,Thierry Valet,Jairo Sinova,Matthias Sitte,Artem Abanov

doi:10.1088/1367-2630/aa8569

Abstract

Topological magnetic textures—like skyrmions—are major players in the design of next-generation magnetic storage technology due to their stability and the control of their motion by ultra-low currents. A major challenge to develop new skyrmion-based technologies is the controlled creation of magnetic skyrmions without the need of complex setups. We show how to create skyrmions and other magnetic textures in ferromagnetic thin films by means of a homogeneous DC current and without requiring Dzyaloshinskii–Moriya interactions. This is possible by exploiting a static loss of stability arising from the interplay of current-induced spin-transfer-torque and a spatially inhomogeneous magnetization, which can be achieved, e.g., by locally engineering the anisotropy, the magnetic field, or other magnetic interactions. The magnetic textures are created controllably and efficiently with a period that can be tuned by the applied current strength. We propose a specific experimental setup realizable with simple materials, such as cobalt based materials, to observe the periodic formation of skyrmions. We show that adding chiral interactions will not influence the basics of the generations but the consequent dynamics w.r.t. the stabilization of topological textures. Our findings allow for skyrmion production on demand in simple ferromagnetic thin films by homogeneous DC currents.

Highlights

Technologies based on spintronics have become integral parts of our world
Magnetic storage devices based on the racetrack memory idea, where traditionally the information is encoded via magnetic domain walls, has been proposed as a design of ultra-dense, low-cost and low-power storage technologies.[1]
Skyrmions are interesting for device relevant systems due to their special properties: i) Skyrmions are particle like and are usually repelled by smooth boundaries, so they do not touch the edges of the sample as domain walls always do; ii) they are topologically non-trivial and more stable than other magnetic textures; iii) they can be efficiently manipulated by ultra-low electric currents,[19,20,21,22,23,24] much smaller than the currents needed to move domain walls in magnetic wires; and iv) the spacing between bits could be of the order of the skyrmion diameter, which allows for a much denser storage compared to domain walls.[2]

Summary

Introduction

Technologies based on spintronics have become integral parts of our world. Current massmarket magnetic memory technologies primarily rely on spintronic devices that couple to the magnetic fields created by domains, which brings inherent limits in storage density and speed. Magnetic storage devices based on the racetrack memory idea, where traditionally the information is encoded via magnetic domain walls, has been proposed as a design of ultra-dense, low-cost and low-power storage technologies.[1] several difficulties arise to efficiently control the domain walls: i) large current densities are needed to move them; ii) nanowires of high quality are required as edge roughnesses will modify the shape of the domain walls or even destroy them; and iii) the spacing between two magnetic domains can hardly be reduced below 30-40 nm.[2]. Skyrmions are interesting for device relevant systems due to their special properties: i) Skyrmions are particle like and are usually repelled by smooth boundaries, so they do not touch the edges of the sample as domain walls always do; ii) they are topologically non-trivial and more stable than other magnetic textures; iii) they can be efficiently manipulated by ultra-low electric currents,[19,20,21,22,23,24] much smaller than the currents needed to move domain walls in magnetic wires; and iv) the spacing between bits could be of the order of the skyrmion diameter, which allows for a much denser storage compared to domain walls.[2]

Results

Discussion

Conclusion