Conference Presentation (After Call)

FZJ-2026-05274

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Tilted and Twisted Magnetic Moments in the Kitaev Magnet α-RuCl3

Wang, X. ; Zhu, F. ; Braden, M. ; Schmalzl, K.FZJ* ; Schmidt, W.FZJ* ; Meven, M.FZJ* ; Feng, E. ; Zhu, Y.FZJ* ; Bertin, A. ; Steffens, P. ; Su, Y. (Corresponding author)FZJ*

2026

Abstract: The layered honeycomb magnet α-RuCl3 has attracted intense scrutiny as a prime candidate for realizing the Kitaev quantum spin liquid, yet a consensus on its spin Hamiltonian remains elusive due to the material’s extreme sensitivity to subtle structural details. Here, we report a comprehensive re-examination of the low-temperature crystallographic and magnetic structures of high-quality α-RuCl3 single crystals using unpolarized and polarized neutron diffraction [1]. We confirm a sharp, first-order structural phase transition to the rhombohedral R-3 space group with a pronounced thermal hysteresis. Crucially, using both spherical and longitudinal neutron polarization analysis, we determine the 3D orientation of the ordered magnetic moment without the ambiguity typically arising from domain distributions. We find that the Ru3+ magnetic moments in the zigzag ordered phase are tilted by 15.7 degrees out of the hexagonal plane and, remarkably, exhibit an additional in-plane twist of −13.8 degrees. This “tilted and twisted” geometry differentiates the ground state from the previously reported models based on unpolarized neutron diffraction or resonant elastic X-ray scattering (REXS) analysis. Furthermore, in combination with our recent polarized inelastic neutron scattering experiment that reveals strong anisotropy of magnetic correlations [2], new insights on the magnetic ground state and the role of the fully anisotropic and bond-direction dependent Kitaev interactions in this compound will be discussed. (Ref: [1] X. Wang et al., Chin. Phys. Lett. 43, 050706 (2026).[2] M. Braden et al., Phys. Rev. Lett. 134, 236702 (2025).)

Keyword(s): Magnetic Materials (1st) ; Magnetism (2nd)

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Contributing Institute(s):

1. JCNS-FRM-II (JCNS-FRM-II)
2. JCNS-4 (JCNS-4)
3. Heinz Maier-Leibnitz Zentrum (MLZ)

Research Program(s):

1. 6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ) (POF4-6G4) (POF4-6G4)
2. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)

Experiment(s):

1. ILL-IN12: Cold neutron 3-axis spectrometer
2. Measurement at external facility

Appears in the scientific report 2026

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