  Chirality plays a major role in nature, from particle physics to DNA, and its
control is much sought-after due to the scientific and technological
opportunities it unlocks. For magnetic materials, chiral interactions between
spins promote the formation of sophisticated swirling magnetic states such as
skyrmions, with rich topological properties and great potential for future
technologies. Currently, chiral magnetism requires either a restricted group of
natural materials or synthetic thin-film systems that exploit interfacial
effects. Here, using state-of-the-art nanofabrication and magnetic X-ray
microscopy, we demonstrate the imprinting of complex chiral spin states via
three-dimensional geometric effects at the nanoscale. By balancing dipolar and
exchange interactions in an artificial ferromagnetic double-helix
nanostructure, we create magnetic domains and domain walls with a well-defined
spin chirality, determined solely by the chiral geometry. We further
demonstrate the ability to create confined 3D spin textures and topological
defects by locally interfacing geometries of opposite chirality. The ability to
create chiral spin textures via 3D nano-patterning alone enables exquisite
control over the properties and location of complex topological magnetic
states, of great importance for the development of future metamaterials and
devices in which chirality provides enhanced functionality.
