Transmission XMCD-PEEM imaging of an engineered vertical FEBID cobalt nanowire with a domain wall

Abstract

).Using focused electron-beam-induced deposition (FEBID), we fabricate vertical, platinum-coated cobalt nanowires with a controlled threedimensional structure. The latter is engineered to feature bends along the height: these are used as pinning sites for domain walls, the presence of which we investigate using X-ray Magnetic Circular Dichroism (XMCD) coupled to PhotoEmission Electron Microscopy (PEEM). The vertical geometry of our sample combined with the low incidence of the X-ray beam produce an extended wire shadow which we use to recover the wire's magnetic configuration. In this transmission configuration, the whole sample volume is probed, thus circumventing the limitation of PEEM to surfaces. This article reports on the first study of magnetic nanostructures standing perpendicular to the substrate with XMCD-PEEM. The use of this technique in shadow mode enabled us to confirm the presence of a domain wall (DW) without direct imaging of the nanowire.

New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures

“…[9,24,25,317,318] While these methods are limited to the analysis of simple magnetic geometries, the visualization of complex 3D shape geometries requires the utilization of the tomographic-based approaches. Thus, MOKE microscopy, [248] that recently was enabled for tomography-like screening of bulk samples; [319] XMCD-PEEM was successfully extended to image interior magnetization textures of complex curved magnetic nanoobjects by using transmission shadow contrasts, [26,181,235,261,262,264,268,[320][321][322] see Figure 8i. X-ray spectro-holography [289] could be also utilizes for the characterization of 3D curved magnetic nanostructures (Figure 8j), for example, magnetically capped nanospheres.…”

Layer-by-Layer Growth of Complex-Shaped Three-Dimensional Nanostructures with Focused Electron Beams

“…[30][31][32] These advances have already led to a number of important fundamental studies in plasmonics, 14,33 photonic crystals, 34 and magnetic nanowires and lattices. [35][36][37][38][39] Beyond nanoprototyping, a substantial increase in throughput for this technique could be accomplished by orders-of-magnitude increases in deposition rates through optimizations of gas injection systems (GIS) 40 and deposition at cryogenic temperatures, 41 and even parallelizing via multiple beams in next-generation tools. 42 The application of FEBID for 3D nanofabrication has progressed significantly in recent years by evolving from a trial-and-error approach to systematic generation of electron beam instructions via CAD software solutions.…”

Domain wall automotion in three-dimensional magnetic helical interconnectors

“…By combining state-of-the-art 3D nanoprinting 3 and standard physical vapor deposition, we prototype 3D helical DW conduits. We observe the automotion of DWs by imaging their magnetic state under different field sequences using X-ray microscopy [4][5][6][7][8] , observing a robust unidirectional motion of DWs from the bottom to the top of the spirals. From experiments and micromagnetic simulations, we determine that the large thickness gradients present in the structure are the main mechanism for 3D DW automotion.…”

“…For the magnetic layer, we use 50 nm of permalloy (Ni 80 Fe 20 ) due to its low coercive fields, and good DW conduit properties 26,27 . We sandwich the permalloy layer with 5 nm Al layers to prevent oxidation, and add a 10 nm Au capping layer that serves as a highly efficient source of photoelectrons in shadow-PEEM and suppresses the XMCD signal from the Py on the substrate 8 .…”

“…Having determined the dominant mechanism for DW automotion in the 3D interconnectors under investigation, we next use shadow X-ray magnetic circular dichroism photoemission electron microscopy (shadow-XPEEM) to experimentally investigate the automotion predicted by simulations. In shadow-XPEEM, the photoelectrons excited by the X-rays are measured in the shadow of the structure, exploiting X-ray magnetic circular dichroism (XMCD) to probe the magnetization parallel to the incident beam 4,8 . Since our structure has a complex 3D shape, interpreting the contrast is not trivial.…”