Individual skyrmion manipulation by local magnetic field gradients

Arianna Casiraghi,Gianfranco Durin,Gerhard Jakob,Olga Kazakova,Felipe Garcia-Sanchez,Mathias Kläui,Mehran Vafaee,Massimo Pasquale,Héctor Corte-León

doi:10.1038/s42005-019-0242-5

Abstract

Magnetic skyrmions are topologically protected spin textures, stabilised in systems with strong Dzyaloshinskii-Moriya interaction (DMI). Several studies have shown that electrical currents can move skyrmions efficiently through spin-orbit torques. While promising for technological applications, current-driven skyrmion motion is intrinsically collective and accompanied by undesired heating effects. Here we demonstrate a new approach to control individual skyrmion positions precisely, which relies on the magnetic interaction between sample and a magnetic force microscopy (MFM) probe. We investigate perpendicularly magnetised X/CoFeB/MgO multilayers, where for X = W or Pt the DMI is sufficiently strong to allow for skyrmion nucleation in an applied field. We show that these skyrmions can be manipulated individually through the local field gradient generated by the scanning MFM probe with an unprecedented level of accuracy. Furthermore, we show that the probe stray field can assist skyrmion nucleation. Our proof-of-concepts results pave the way towards achieving current-free skyrmion control.

Highlights

Magnetic skyrmions are topologically protected spin textures, stabilised in systems with strong Dzyaloshinskii-Moriya interaction (DMI)
We show that isolated skyrmions can be manipulated individually and precisely using the local field gradient generated by a magnetic force microscopy (MFM) probe in ultra-thin films with perpendicular magnetic anisotropy (PMA)
Since MFM was used to investigate the magnetic configuration for all sample stacks, as well as to image, nucleate, and manipulate individual skyrmions, it is important to assess the effects of probe–sample interaction during

Summary

Introduction

Magnetic skyrmions are topologically protected spin textures, stabilised in systems with strong Dzyaloshinskii-Moriya interaction (DMI). In magnetic systems with large spin–orbit coupling and lack of structural inversion symmetry, the Dzyaloshinskii-Moriya interaction (DMI)[1,2] can be strong enough to stabilise non-collinear spin textures, most notably magnetic skyrmions Since their first discovery in chiral magnets[3,4], magnetic skyrmions have attracted significant attention within the spintronics community due to their fascinating properties and potential applications[5,6]. By exploiting the probe–sample interaction skyrmions can be moved in standard two pass MFM mode, through the local field gradient generated by the probe This technique allows for the reversible and controllable manipulation of individual skyrmions, contrary to more conventional current-driven motion where skyrmions move in a collective manner. We show that the probe–sample interaction can be used to create individual skyrmions at magnetic fields lower than their intrinsic nucleation field, by either collapsing stripe domains into skyrmions or by directly cutting through the stripe domains to generate skyrmions

Methods

Results

Conclusion