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arXiv · 2512.07183

Spin and Orbital Magnetism in UH2 Thin Films Studied by X-ray Magnetic Circular Dichroism

Evgenia A. Tereshina-Chitrova·Mykhaylo Paukov·Oleksandra Koloskova·Amir Hen·Fabrice Wilhelm·Lukas Horak·Mayerling Martinez Celis·Miroslav Cieslar·Ladislav Havela·Andrei Rogalev·Thomas Gouder
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Abstract

Uranium dihydride UH2 is a metastable phase unknown in bulk form but accessible through thin-film synthesis. We prepared UH2 films by reactive dc sputtering on CaF2(001) or Si(001) substrates, the latter equipped with a Mo buffer layer to suppress a U-Si interdiffusion. On CaF2, UH2 adopts the fluorite-type structure with a near-[1 1 1] out-of-plane texture, four rotational domains, and a lattice parameter a = 539 +- 3 pm without measurable strain, whereas the Mo-buffered film is polycrystalline. X-ray photoelectron spectroscopy confirmed complete hydrogenation and minimal oxidation. Magnetization and XMCD measurements show ferromagnetic ordering with Curie temperatures of 120-130 K and a uranium 5f moment of 0.9 {\mu}B/U, dominated by the orbital contribution ({\mu}L ~ 1.4 {\mu}B, {\mu}S ~ -0.5 {\mu}B), in a good agreement with GGA+U computations, which otherwise overestimate absolute values of the spin and orbital components. The slightly reduced moment in thinner CaF2-supported films is attributed to surface U(IV) species. These results demonstrate that thin-film synthesis enables stabilization of UH2 and direct probing of 5f magnetism, opening pathways toward higher uranium hydrides and interface-engineered actinide systems.

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Evgenia A. Tereshina-Chitrova, Mykhaylo Paukov, Oleksandra Koloskova, Amir Hen, Fabrice Wilhelm, Lukas Horak, Mayerling Martinez Celis, Miroslav Cieslar, Ladislav Havela, Andrei Rogalev, Thomas Gouder. 2025-12-08. Spin and Orbital Magnetism in UH2 Thin Films Studied by X-ray Magnetic Circular Dichroism. https://arxiv.org/abs/2512.07183

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