Chirality Imprinting and Spin-texture Tunability in Conformally Coated 3D Magnetic Nanostructured Metamaterials

Abstract

Three-dimensional (3D) magnetic nanostructures offer unprecedented opportunities for engineering emergent spin textures, but controlling their configuration remains a central challenge. Here we show that conformally coated Ni Nanotubes arranged in a woodpile geometry with lattice spacings ranging from 800 to 1200 nm, realised by two-photon lithography and atomic layer deposition, exhibit a geometry-tuneable balance between chiral and axial states. Magnetic force microscopy on the top layer of the 3D woodpile reveals that few-layer systems exhibit a chiral contrast whilst increasing the number of stacked layers drives a transition to an axial configuration with the change in state populations depending strongly on lattice spacing. Micromagnetic simulations demonstrate that chirality is not intrinsic to isolated tubes but is imprinted by spin textures formed in the substrate sheet film, which couple into the 3D network. As the sheet-film influence diminishes with increasing layer number, dipolar interactions dominate and stabilise the axial state. This two-stage mechanism of chirality imprinting followed by increasingly dominant dipolar interactions, provides clear control parameters for tailoring spin-texture populations. Our results establish conformally coated woodpiles as a reconfigurable 3D ferromagnetic metamaterial platform that can be exploited for data storage, magnonics, and neuromorphic computing.