Polarized neutron scattering as a probe for vortex-type spin correlations in iron oxide multicore assemblies

Venus Rai; Ivan Titov; Elizabeth M. Jefremovas; Štefan Liščák; Sivarenjini Shan; Nina-Juliane Steinke; Jonathan Leliaert; Álvaro Gallo-Córdova; María P. Morales; Davide Peddis; Pierfrancesco Maltoni; Luis Fernández Barquín; Andreas Michels; Michael P. Adams

arXiv · 2606.18791

Polarized neutron scattering as a probe for vortex-type spin correlations in iron oxide multicore assemblies

Venus Rai·Ivan Titov·Elizabeth M. Jefremovas·Štefan Liščák·Sivarenjini Shan·Nina-Juliane Steinke·Jonathan Leliaert·Álvaro Gallo-Córdova·María P. Morales·Davide Peddis·Pierfrancesco Maltoni·Luis Fernández Barquín·Andreas Michels·Michael P. Adams

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Abstract

We report an experimental investigation of the magnetic microstructure of iron oxide multicore assemblies by means of polarized small-angle neutron scattering (SANS). Guided by a recently developed analytical theory for vortex-state magnetic nanoparticles, we provide a quantitative comparison between the measured and calculated cross sections, revealing signatures that are consistent with vortex-type magnetization configurations at low applied magnetic fields. In particular, the field evolution and the characteristic isotropic ring-type feature of the spin-flip scattering intensity at intermediate momentum transfers are in line with the formation of flux-closure states. The latter are stabilized by the interplay of exchange, Zeeman, and magnetostatic energies. The methodology allows for a statistically significant characterization of vortex states in densely packed nanoparticle systems, thereby complementing surface-sensitive techniques that are commonly limited to the observation of spin structures in individual particles.

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Venus Rai, Ivan Titov, Elizabeth M. Jefremovas, Štefan Liščák, Sivarenjini Shan, Nina-Juliane Steinke, Jonathan Leliaert, Álvaro Gallo-Córdova, María P. Morales, Davide Peddis, Pierfrancesco Maltoni, Luis Fernández Barquín, Andreas Michels, Michael P. Adams. 2026-06-17. Polarized neutron scattering as a probe for vortex-type spin correlations in iron oxide multicore assemblies. https://arxiv.org/abs/2606.18791

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