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Nano Lett. 2018 Apr 11;18(4):2263-2267. doi: 10.1021/acs.nanolett.7b04802. Epub 2018 Mar 19.

Halbach Effect at the Nanoscale from Chiral Spin Textures.

Author information

1
Empa, Swiss Federal Laboratories for Materials Science and Technology , CH-8600 Dübendorf , Switzerland.
2
Center for Nanoscale Science and Technology , National Institute of Standards and Technology , Gaithersburg , Maryland 20899 , United States.
3
Department of Physics , University of Basel , CH-4056 Basel , Switzerland.

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 and magnetic levitation trains, but exploiting Halbach arrays in micro- or nanoscale spintronics devices requires solving the problem of fabrication and field metrology below a 100 μm size. In this work, we show that a Halbach configuration of moments can be obtained over areas as small as 1 μm × 1 μm in sputtered thin films with Néel-type domain walls of unique domain wall chirality, and we measure their stray field at a controlled probe-sample distance of 12.0 ± 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. Skyrmions (<100 nm wide) 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.

KEYWORDS:

Dyzaloshinkii−Moriya interaction; Halbach effect; Thin-film magnetism; magnetic force microscopy; skyrmions

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