Probing the pinning strength of magnetic vortex cores with sub-nanometer resolution

Markus Morgenstern,Christian Holl,Marvin Knol,Samir Lounis,Marco Pratzer,Jonathan Chico,Imara Lima Fernandes

doi:10.1038/s41467-020-16701-y

Markus Morgenstern, Christian Holl + Show 5 more

Open Access

https://doi.org/10.1038/s41467-020-16701-y

Copy DOI

Abstract

Understanding interactions of magnetic textures with defects is crucial for applications such as racetrack memories or microwave generators. Such interactions appear on the few nanometer scale, where imaging has not yet been achieved with controlled external forces. Here, we establish a method determining such interactions via spin-polarized scanning tunneling microscopy in three-dimensional magnetic fields. We track a magnetic vortex core, pushed by the forces of the in-plane fields, and discover that the core (~ 104 Fe-atoms) gets successively pinned close to single atomic-scale defects. Reproducing the core path along several defects via parameter fit, we deduce the pinning potential as a mexican hat with short-range repulsive and long-range attractive part. The approach to deduce defect induced pinning potentials on the sub-nanometer scale is transferable to other non-collinear spin textures, eventually enabling an atomic scale design of defect configurations for guiding and reliable read-out in race-track type devices.

Highlights

Understanding interactions of magnetic textures with defects is crucial for applications such as racetrack memories or microwave generators
We reproduce the measured core path along several defects via superposing pinning potentials, each consisting of an attractive part with amplitude 200 meV originating from an absent exchange energy and an even stronger repulsive part of unknown origin
Employing simulations based on density functional theory (DFT), we investigated the impact of single Cr and O adatoms on the magnetic properties of Fe(110)

Summary

Introduction

Understanding interactions of magnetic textures with defects is crucial for applications such as racetrack memories or microwave generators Such interactions appear on the few nanometer scale, where imaging has not yet been achieved with controlled external forces. The approach to deduce defect induced pinning potentials on the sub-nanometer scale is transferable to other non-collinear spin textures, eventually enabling an atomic scale design of defect configurations for guiding and reliable read-out in race-track type devices. We apply well defined lateral forces by in-plane magnetic fields B∥24 and independently tune the size of the vortex core by an out-of-plane field B⊥ The latter enables control on the non-collinearity of the core magnetization and, on the strength of exchange energy density uexch in the core. We reproduce the measured core path along several defects via superposing pinning potentials, each consisting of an attractive part with amplitude 200 meV originating from an absent exchange energy and an even stronger repulsive part of unknown origin

Methods

Results

Conclusion