Complex free-space magnetic field textures induced by three-dimensional magnetic nanostructures

Abstract

The design of complex, competing effects in magnetic systems—be it via the introduction of nonlinear interactions1–4, or the patterning of three-dimensional geometries5,6—is an emerging route to achieve new functionalities. In particular, through the design of three-dimensional geometries and curvature, intrastructure properties such as anisotropy and chirality, both geometry-induced and intrinsic, can be directly controlled, leading to a host of new physics and functionalities, such as three-dimensional chiral spin states7, ultrafast chiral domain wall dynamics8–10 and spin textures with new spin topologies7,11. Here, we advance beyond the control of intrastructure properties in three dimensions and tailor the magnetostatic coupling of neighbouring magnetic structures, an interstructure property that allows us to generate complex textures in the magnetic stray field. For this, we harness direct write nanofabrication techniques, creating intertwined nanomagnetic cobalt double helices, where curvature, torsion, chirality and magnetic coupling are jointly exploited. By reconstructing the three-dimensional vectorial magnetic state of the double helices with soft-X-ray magnetic laminography12,13, we identify the presence of a regular array of highly coupled locked domain wall pairs in neighbouring helices. Micromagnetic simulations reveal that the magnetization configuration leads to the formation of an array of complex textures in the magnetic induction, consisting of vortices in the magnetization and antivortices in free space, which together form an effective B field cross-tie wall14. The design and creation of complex three-dimensional magnetic field nanotextures opens new possibilities for smart materials15, unconventional computing2,16, particle trapping17,18 and magnetic imaging19.

Spatial magnetic imaging of non-axially symmetric vortex domains in cylindrical nanowire by transmission X-ray microscopy

“…[1][2][3] However, the experimental access to 3D morphologies is much more challenging than for planar systems and, so far, research to date has not yet explored all interesting complexities of the vast diversity of three-dimensional spin textures, with a few exceptions. 4,5 In this scenario, magnetic cylindrical nanowires offer a controllable constant surface curvature and a wide range of potential capabilities from both fundamental and technological points of view. [6][7][8] The curvature and confinement of cylindrical nanowires (NW) promote novel non-trivial structures such as Bloch-point domain walls, 9 helical magnetic configurations, 10,11 vortices 12 or skyrmion tubes.…”

“…[14][15][16][17] The current challenge is to determine the magnetization spatial distribution in more complex 3D geometries. 4,5,18,19 For magnetic cylindrical nanowires, TXM-XMCD techniques are very promising for the access to detailed information of 3D magnetization configurations since this technique probes the full inner wire and not only its surface.…”

Modified Spin Textures in a 3D Magnetic Lattice

“…Writing the desired multivortex states on the multilayered nanowires demonstrated potential for the future 3D information storage device. Beyond conventional cylindrical nanowires, double helix 3D magnetic nanostructures, made up of two intertwined nanowires, have been reported by Donnelly et al [ 23 ] They observed interesting magnetic behavior through these unique magnetic double helices and managed to introduce nonlinear magnetic interactions into the 3D system. May et al worked on a 3D artificial spin‐ice system fabricated by two‐photon lithography.…”

Searching for new ferromagnetism precursors in two-dimensional model materials in frame of local force theorem

“…Nowadays the global trend of miniaturization and ecologization in science and industry pushes the progress towards utilizing the low-dimensional physical systems, such as single-layered crystal structures and clusters of individual adatoms. It manifest itself as naturally coming substitution of traditional unit electronic elements [1][2][3]. Indeed, we observe the tremendous and constantly growing number of theoretical and experimental studies, devoted to discovering novel physical mechanisms and special systems to be applied as the computer memory cell or elementary arithmetic device [4][5][6][7][8].…”