Direct-write of free-form building blocks for artificial magnetic 3D lattices

Abstract

By the fabrication of periodically arranged nanomagnetic systems it is possible to engineer novel physical properties by realizing artificial lattice geometries that are not accessible via natural crystallization or chemical synthesis. This has been accomplished with great success in two dimensions in the fields of artificial spin ice and magnetic logic devices, to name just two. Although first proposals have been made to advance into three dimensions (3D), established nanofabrication pathways based on electron beam lithography have not been adapted to obtain free-form 3D nanostructures. Here we demonstrate the direct-write fabrication of freestanding ferromagnetic 3D nano-architectures. By employing micro-Hall sensing, we have determined the magnetic stray field generated by our free-form structures in an externally applied magnetic field and we have performed micromagnetic and macro-spin simulations to deduce the spatial magnetization profiles in the structures and analyze their switching behavior. Furthermore we show that the magnetic 3D elements can be combined with other 3D elements of different chemical composition and intrinsic material properties.

Hopfions in a lattice dimer model

“…realizing ASI on a cubic lattice with simultaneous magnetization flips around each square plaquette, may result in realizing ASI, which dynamics is the same as considered in this paper. Finally, we mention, that in the recent years, there were numerous efforts to create 3D artificial spin ice [29][30][31], and we emphasize that creating hopfions requires a lattice with just two layers.…”

Tailoring Magnetic Anisotropy at Will in 3D Interconnected Nanowire Networks

“…The fabrication method of such 3D interlinked nanostructures is based on porous alumina membranes filled via electrochemical deposition, which constitutes a low‐cost method, is highly tunable, with no need of vacuum or atmosphere‐controlled environment, and is easily scalable to the industry. Other methods of obtaining 3D nanostructures are ion‐track‐etched polymeric membranes (however, by this technique, certain parameters cannot be controlled, such as the exact number and position of interconnections between NWs), two‐photon lithography, or focused electron beam‐induced deposition (which are comparably much more expensive and time‐consuming). Nevertheless, these methods have the advantage of being able to produce more complex 3D structures of virtually any magnetic material.…”

Single‐Electron Effects for Probing Local Electrical Polarization Changes and Charge Hopping

“…At this point we argue that surface oxidation of the Co 3 Fe islands, which cannot be avoided during transfer of the samples through air between fabrication and insertion into the cryostate, may be responsible for the reduced threshold voltage. In fact, transmission electron microscopy in conjunction with elemental analysis indicates that a spinel‐like oxide layer forms on the surface of Co 3 Fe FEBID structures . In order to take this semi‐quantitatively into account we modify our model and assume a 1 nm oxide layer around each metallic sphere such that the metallic core diameter is reduced to 13 nm and the overall diameter of the spheres remains at 15 nm.…”