Halbach arrays at the nanoscale from chiral spin textures

TL;DR

This paper demonstrates the creation of nanoscale Halbach arrays using chiral spin textures in thin films, enabling controlled magnetic field manipulation at the nanometer scale for potential spintronics applications.

Contribution

It introduces a method to realize Halbach configurations at the nanoscale using chiral spin textures driven by interfacial Dzyaloshinskii-Moriya interaction in sputtered films.

Findings

Achieved Halbach-like magnetic configurations in 1x1 μm² areas.

Measured stray fields at nanometer probe-sample distances.

Demonstrated control of magnetic field funneling with skyrmions.

Abstract

Mallinson's idea that some spin textures in planar magnetic structures could produce an enhancement of the magnetic flux on one side of the plane at the expense of the other gave rise to permanent magnet configurations known as Halbach magnet arrays. Applications range from wiggler magnets in particle accelerators and free electron lasers, to motors, to magnetic levitation trains, but exploiting Halbach arrays in micro- or nanoscale spintronics devices requires solving the problem of fabrication and field metrology below 100 {\mu}m size. In this work we show that a Halbach configuration of moments can be obtained over areas as small as 1 x 1 {\mu}m^2 in sputtered thin films with N\'eel-type domain walls of unique domain wall chirality, and we measure their stray field at a controlled probe-sample distance of 12.0 x 0.5 nm. Because here chirality is determined by the interfacial Dyzaloshinkii-Moriya interaction the field attenuation and amplification is an intrinsic property of this film, allowing for flexibility of design based on an appropriate definition of magnetic domains. 100 nm-wide skyrmions illustrate the smallest kind of such structures, for which our measurement of stray magnetic fields and mapping of the spin structure shows they funnel the field toward one specific side of the film given by the sign of the Dyzaloshinkii-Moriya interaction parameter D.