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arxiv: 2605.14673 · v1 · pith:CBBBH3FAnew · submitted 2026-05-14 · ❄️ cond-mat.mes-hall · cond-mat.mtrl-sci

Compositional and Magnetic Characterisation of Oblique Co and Fe Nanowire Structures Fabricated Using Focused Electron Beam Induced Deposition

Aurys Silinga , Keir Edgar , Stephen McVitie , Kayla Fallon , Andr\'as Kov\'acs , Rafal E. Dunin-Borkowski , Trevor P. Almeida This is my paper

Pith reviewed 2026-06-30 20:32 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall cond-mat.mtrl-sci
keywords FEBIDnanowirescobaltironmetal contentmagnetic inductionoblique growthelectron holography
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The pith

Tuning electron beam voltage and current lets FEBID produce Co and Fe nanowires with roughly equal metal content at growth angles up to 60 degrees.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper studies how growth angle changes the metal content and magnetic properties of cobalt and iron nanowires made by focused electron beam induced deposition. Metal content falls with steeper angles because the electron beam interacts with a larger volume of material. The authors demonstrate that the lowest workable beam voltage combined with the highest current largely removes this drop, producing nanowires whose metal fraction and magnetic induction stay approximately constant from 0 to 60 degrees. This result matters for building complex three-dimensional nanoscale devices such as spintronic components that contain overhanging or bridged features. Measurements on 41 test structures used electron energy loss spectroscopy to track composition and off-axis electron holography to track magnetic induction.

Core claim

Ferromagnetic NWs with approximately equal metal content at growth angles from 0° to 60° were fabricated by using the lowest viable electron beam voltage and the highest viable beam current to reduce the interaction volume and increase the metal content, respectively. Comparison of the results reveals a reduction in metal content with increased oblique growth angle in FEBID NWs. The magnitude of metal content reduction can be tuned by controlling electron beam parameters.

What carries the argument

FEBID growth of Co and Fe nanowires at controlled oblique angles, with atomic composition mapped by electron energy loss spectroscopy and magnetic induction mapped by off-axis electron holography.

If this is right

  • Metal content in FEBID nanowires decreases as the oblique growth angle increases.
  • The size of the metal-content reduction can be controlled by changing electron beam voltage and current.
  • Optimized low-voltage, high-current beams produce nanowires with nearly constant metal content from 0° to 60°.
  • Magnetic induction varies in step with the measured changes in metal content.
  • Structures with overhanging or bridged elements can be grown with more uniform composition.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same beam-parameter choice may allow uniform composition in other FEBID materials beyond Co and Fe.
  • Complex 3D spintronic prototypes could be made without later correction steps for composition gradients.
  • Further reduction of interaction volume might extend uniform growth beyond 60 degrees.
  • Reliability of magnetic devices built from such nanowires could improve if composition is held constant.

Load-bearing premise

The observed drop in metal content is caused primarily by growth angle and interaction volume rather than by other uncontrolled variables in the deposition process or in the microscopy measurements.

What would settle it

Growing nanowires at 60 degrees with the lowest viable voltage and highest viable current and measuring substantially lower metal content than in 0-degree nanowires would show that equal content cannot be maintained.

Figures

Figures reproduced from arXiv: 2605.14673 by Andr\'as Kov\'acs, Aurys Silinga, Kayla Fallon, Keir Edgar, Rafal E. Dunin-Borkowski, Stephen McVitie, Trevor P. Almeida.

Figure 1
Figure 1. Figure 1: FEBID 3D printing process. (a) Schematic diagram of FEBID process, where NW structures [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: SE SEM images of FEBID NWs that are characterised and compared. (a) [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Model of NW atomic composition. (a) Calculation of a compositional map, assuming the NW [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Comparison of vertical Co FEBID NWs deposited at 30 kV. (a-c) Vertical NWs from samples [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Measurement of cross-section shape and Co content for the [PITH_FULL_IMAGE:figures/full_fig_p010_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Variation in oblique NW composition and shape as a function of growth angle. (a) SE SEM images [PITH_FULL_IMAGE:figures/full_fig_p011_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Micromagnetic simulations of FEBID Co cylinders. (a), (b), (c) correspond, respectively, to 80 nm, [PITH_FULL_IMAGE:figures/full_fig_p012_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Magnetic characterisation of the Co↗ 5 kV sample. (a) Magnetic induction map with contour spacings of 2π/5 rad. (b) Line traces of φm are from areas corresponding to the white boxes in (a). The measured φm gradient is consistently smaller for higher θ. The central band is denoted by dashed lines. (c) Correlation between θ and By in the central band [PITH_FULL_IMAGE:figures/full_fig_p013_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Magnetic characterisation of the Fe↗ 30 kV sample. (a) Magnetic induction map with contour spacings of 2π/5 rad. (b) Line traces of φm are from areas corresponding to the white boxes in (a). The measured φm gradient is consistently smaller for higher θ. The central band is denoted by dashed lines. (c) Correlation between θ and By in the central band. 13 [PITH_FULL_IMAGE:figures/full_fig_p013_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Correlations between NW metal content and associated magnetic properties. (a) Correlation [PITH_FULL_IMAGE:figures/full_fig_p014_10.png] view at source ↗
read the original abstract

Focused electron beam induced deposition (FEBID) is an additive manufacturing technique uniquely suited for fabricating nanoscale 3D prototypes for a range of applications, including spintronic devices. However, the variation of growth dynamics associated with electron beam translation and sample interaction volumes results in structures with non-uniform composition when fabricating intricate 3D geometries. Herein, we measure changes in atomic composition and corresponding changes in magnetic induction in 3D ferromagnetic nanostructures with overhanging elements, e.g. bridges or arches. To investigate the effects of electron beam translation, we fabricated 41 Co and Fe nanowire (NW) structures with growth angle relative to the optic axis varying from 0{\deg} to 90{\deg}. The (scanning) transmission electron microscopy techniques of electron energy loss spectroscopy and off-axis electron holography were performed to map the NW elemental composition and magnetic induction as a function of NW growth angle. Comparison of the results reveals a reduction in metal content with increased oblique growth angle in FEBID NWs. The magnitude of metal content reduction can be tuned by controlling electron beam parameters, and ferromagnetic NWs with approximately equal metal content at growth angles from 0{\deg} to 60{\deg} were fabricated by using the lowest viable electron beam voltage and the highest viable beam current to reduce the interaction volume and increase the metal content, respectively.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 3 minor

Summary. The manuscript reports fabrication of 41 Co and Fe nanowire structures by FEBID with growth angles from 0° to 90° relative to the optic axis. Using EELS and off-axis electron holography, the authors map atomic composition and magnetic induction versus angle, observe a reduction in metal content at higher oblique angles, and claim that this reduction can be compensated by selecting the lowest viable beam voltage and highest viable beam current, yielding approximately equal metal content for angles from 0° to 60°.

Significance. If the compensation result holds, the work provides a practical parameter-based route to uniform-composition 3D ferromagnetic nanostructures, directly relevant to spintronic device prototyping where angle-dependent interaction volumes otherwise produce non-uniform metal content. The direct correlation of composition maps with magnetic induction measurements strengthens the link between fabrication parameters and functional properties.

minor comments (3)
  1. [Abstract] Abstract: the statement that 'ferromagnetic NWs with approximately equal metal content at growth angles from 0° to 60° were fabricated' would be strengthened by explicit numerical values (or a table) for the measured metal fractions at each angle together with the number of structures measured per angle.
  2. [Methods] The manuscript does not state the specific beam voltage and current values chosen as 'lowest viable' and 'highest viable', nor the criteria used to define viability; these parameters are central to the reported compensation method.
  3. [Results] Figure captions and text should clarify whether error bars or standard deviations are shown on composition or induction plots and how many independent measurements contribute to each data point.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the positive assessment of our work on FEBID Co and Fe nanowires and for recommending minor revision. The manuscript demonstrates that oblique growth angles reduce metal content but that this can be compensated via low voltage and high current to achieve approximately uniform metal content from 0° to 60°.

Circularity Check

0 steps flagged

No significant circularity

full rationale

The manuscript is a purely experimental characterization paper. It fabricates nanowires at controlled angles, then applies standard EELS and off-axis holography to measure composition and magnetic induction directly. No equations, fitted parameters, predictive models, or self-citations appear in the load-bearing claims. The reported ability to tune metal content by beam voltage and current is presented as an empirical outcome of the chosen growth conditions, not as a derivation that reduces to its own inputs. The work is therefore self-contained against external benchmarks with no circular steps.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Experimental materials characterization paper; no free parameters, mathematical axioms, or invented entities are introduced beyond standard physics and established microscopy methods.

pith-pipeline@v0.9.1-grok · 5817 in / 993 out tokens · 35399 ms · 2026-06-30T20:32:41.621186+00:00 · methodology

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