  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.
