Conformally Coated 3D Magnetic Nanostructures Enable Geometry-Dependent Spin Texture Control

Three-dimensional magnetic nanostructures promise revolutionary advances in data storage and magnonics, but achieving precise control over their complex magnetic configurations remains a significant hurdle. Alexander Roberts, Huixin Guo, and Joseph Askey, working with colleagues at CardiI University and EPFL, now demonstrate a method for tuning these magnetic textures within a novel metamaterial.

The team created conformally coated nickel nanotubes arranged in a woodpile structure, and they discovered that the material exhibits a tuneable balance between chiral and axial magnetic states. This control arises from a two-stage process, where initial chirality is imprinted by underlying magnetic textures before dipolar interactions stabilise a more axial configuration as the structure’s layers increase, establishing a reconfigurable platform for future magnetic technologies. Chiral Magnetism in 3D Nickel Nanotubes This research details the creation and investigation of three-dimensional magnetic nanostructures, specifically woodpile lattices constructed from nickel nanotubes. The study focuses on controlling the magnetic textures within these structures, revealing the emergence of both chiral and axial magnetization states. Researchers demonstrated the ability to influence the magnetic configuration of the nanotubes, with the dominant state dependent on the spacing between nanotubes and the number of layers in the woodpile structure. Lower layer counts favour chiral states, while increasing the number of layers promotes axial states. A key finding is the mechanism of chiral imprinting, where a thin magnetic sheet film used during fabrication influences the magnetization of the topmost nanotubes, stabilizing the chiral state. Magnetic force microscopy visualised these textures, confirming the presence of both chiral and axial states, and micromagnetic simulations validated the experimental observations, supporting the proposed mechanism of chiral imprinting.

This research demonstrates a pathway to control the magnetic configuration of three-dimensional nanostructured materials, potentially enabling the development of advanced magnetic devices with tailored properties, and the ability to imprint chirality into the structure is particularly interesting for spintronic applications.,.

Woodpile Nanostructures Fabricated by Atomic Layer Deposition Researchers engineered three-dimensional magnetic nanostructures using a combination of two-photon lithography and atomic layer deposition to create woodpile geometries, enabling precise control over emergent spin textures. This fabrication process involved constructing alternating orthogonally oriented polymer rods, conformally coated with a 30 nanometer thick layer of nickel, resulting in ferromagnetic nanotubes with lateral dimensions of 400 nanometers and axial dimensions of 990 nanometers. Crucially, the atomic layer deposition process also coated exposed substrate, forming a continuous sheet film alongside the woodpile structure. Woodpile structures were fabricated with spacings of 800 nanometers, 1000 nanometers, and 1200 nanometers, varying the number of stacked nanotubes from 3 to 14 layers.

The team partially embedded the structures within the substrate during fabrication, providing mechanical anchoring and ensuring stability, with the uppermost layers protruding above the surface for larger numbers of stacked nanotubes. Scanning electron microscope imaging confirmed the successful fabrication of these structures, revealing the defined spacings and layer arrangements. To investigate the magnetic properties, scientists performed magnetic force microscopy on the woodpile surfaces, first applying a specific magnetic field protocol to establish a consistent field history. The resulting data revealed distinct contrast patterns depending on the number of stacked layers and spacing. Structures with three layers exhibited pronounced phase shifts, indicative of a chiral magnetic state, while structures with 14 layers exhibited regions of constant phase and bright/dark lobes, characteristic of an axial, single-domain configuration. Detailed analysis of MFM measurements across a range of structures with varying layer numbers and spacings generated state maps, demonstrating a clear transition from predominantly chiral states with three layers to predominantly axial states with 14 layers, with the rate of transition dependent on the spacing.

The team observed 97. 2% chiral state for a 1200 nanometer spacing with three layers, decreasing as the number of layers increased.,. Reconfigurable 3D Magnetic Nanotube Networks Visualized Researchers have achieved a breakthrough in engineering three-dimensional magnetic nanostructures, creating reconfigurable metamaterials with precisely controlled spin textures.

The team fabricated woodpile geometries using a combination of two-photon lithography and atomic layer deposition, resulting in networks of nickel nanotubes with lateral dimensions of 400nm and axial dimensions of 990nm. These structures were conformally coated with nickel films having a thickness of 30nm, ensuring uniform magnetic properties throughout the three-dimensional lattice. Experiments utilizing scanning probe microscopy directly visualized local spin textures, revealing a strong dependence of both nanotube magnetization and overall magnetic configuration on the number of stacked layers and the spacing.

The team demonstrated that by varying the spacing, they could tune the magnetic configuration, achieving a transition from chiral to aligned top layer configurations. Specifically, the woodpile structures, with spacings ranging from 800 to 1200nm, exhibited a geometry-tuneable balance between chiral and axial states. Micromagnetic simulations corroborated these findings, revealing a two-stage mechanism governing the observed magnetic behavior. The simulations demonstrated that coupling between the woodpile structure and a conformal sheet film initially imprints chiral spin textures. As the number of stacked layers increases, the influence of this sheet film diminishes, and dipolar interactions become dominant, stabilizing an axial state. This precise control over spin texture populations establishes these conformally coated woodpiles as a novel platform for applications in data storage, magnonics, and neuromorphic computing.,. Geometric Control of Magnetic Texture States This research demonstrates a new method for controlling magnetic textures within three-dimensional nanostructures, specifically using woodpile architectures conformally coated with nickel. Scientists successfully created these structures using advanced lithography and atomic layer deposition, enabling precise control over the arrangement of magnetic nanotubes. Through magnetic force microscopy, they observed that these woodpiles exhibit two distinct spin textures: chiral states, imprinted from the underlying sheet film, and axially aligned states, favoured by dipolar interactions between the nanotubes. Crucially, the balance between these chiral and axial states can be tuned by adjusting the number of stacked nanotubes and the spacing between them. This geometric control establishes these conformally coated woodpiles as a novel class of magnetic metamaterial, offering a pathway to reconfigurable magnetic devices.

The team acknowledges that the influence of the underlying sheet film diminishes with increasing layer number, ultimately leading to the dominance of dipolar interactions, and this interplay is key to understanding the observed behaviour. Future work may focus on exploiting this control for applications in reconfigurable magnonics and spintronics, including the development of devices for neuromorphic and reservoir computing where the geometry-driven magnetic complexity can be harnessed for information processing. 👉 More information 🗞 Chirality Imprinting and Spin-texture Tunability in Conformally Coated 3D Magnetic Nanostructured Metamaterials 🧠 ArXiv: https://arxiv.org/abs/2512.13321 Tags: