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arXiv · 2610.30416

Design of Nuclear and Magnetic Scattering Length Density Profiles

Alexandros Barnasas·Edward J. Stuckey·Alexei A. Vorobiev·Joashaniel F. K. Cooper·Sjoerd Stendahl·Björgvin Hjörvarsson
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Abstract

The scattering length density (SLD) profile of a sample can be deliberately designed to enhance the information of interest obtained from neutron reflectometry. Here, we demonstrate this approach using amorphous $\mathrm{Fe}_{x}\mathrm{Co}_{y}\mathrm{Al}_{8}\mathrm{Zr}_{2}$ thin films. Four samples, each comprising ten repetitions of an AlZr spacer layer and a magnetic layer, were prepared with magnetic-layer compositions of $\mathrm{Fe}_{80}\mathrm{Co}_{10}\mathrm{Al}_{8}\mathrm{Zr}_{2}$, $\mathrm{Fe}_{70}\mathrm{Co}_{20}\mathrm{Al}_{8}\mathrm{Zr}_{2}$, $\mathrm{Fe}_{60}\mathrm{Co}_{30}\mathrm{Al}_{8}\mathrm{Zr}_{2}$, and $\mathrm{Fe}_{45}\mathrm{Co}_{45}\mathrm{Al}_{8}\mathrm{Zr}_{2}$, and characterised using X-ray and polarised neutron reflectometry. Across the series, the nuclear SLD of the FeCoAlZr alloy decreases approximately linearly from $7.14 \times 10^{-6}$ to $4.63 \times 10^{-6}$ $\mathring{\mathrm{A}}^{-2}$ with increasing Co content, while the magnetic SLD is approximately $4.3$-$4.5 \times 10^{-6}$ $\mathring{\mathrm{A}}^{-2}$. These results demonstrate that the nuclear and magnetic contributions can be controlled largely independently, with composition primarily tuning the nuclear SLD and the applied magnetic field offering, in principle, additional control of the magnetic contribution.

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Alexandros Barnasas, Edward J. Stuckey, Alexei A. Vorobiev, Joashaniel F. K. Cooper, Sjoerd Stendahl, Björgvin Hjörvarsson. 2026-10-21. Design of Nuclear and Magnetic Scattering Length Density Profiles. https://arxiv.org/abs/2610.30416

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