Artificial double-helix for geometrical control of magnetic chirality

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 nanopatterning 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.
This work was funded by EPSRC Early Career Fellowship EP/M008517/1, the Winton Program for the Physics of Sustainability, and the EU CELINA COST action. D.S.-H. acknowledges a Girton College Pfeiffer scholarship and support from the EPSRC CDT in Nanoscience and Nanotechnology. A.H.-R. and S.M.V. acknowledge funding from the EU Horizon 2020 program through Marie Skłodowska-Curie Action H2020-MSCA-IF-2016-74695. C.D. acknowledges funding from Leverhulme Trust (ECF-2018-016), Isaac Newton Trust (18-08), and a L’Oréal-UNESCO UK and Ireland Fellowship for Women in Science 2019. Funding by the Spanish Ministry of Science is acknowledged, grants MAT2017-82970-C2-1-R, MAT2017-82970-C2-2-R and MAT2018-102627-T, and by Aragon Government (Construyendo Europa desde Aragón), grant E13_20R including European Social Fund. J.P.-N. acknowledges MINECO funding BES-2015-072950. S.M.V. appreciates support from EPSRC EP/M024423/1. P.F. was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, Contract No. DE-AC02-05-CH11231 (NEMM program MSMAG). These experiments were performed at MISTRAL beamline at ALBA Synchrotron with the collaboration of ALBA staff and CALIPSOplus (Grant 730872) funding.