Tunable inter-bilayer magnetic correlations and candidate multipolar physics in the van der Waals oxyhalides DyOCl, DyOBr, and DyOI

Published

August 19, 2026

Author(s)

F. Brooks, X. Bai, J. Bacsa, M. B. Stone, S. Calder, Nicholas Butch, V. Garlea, M. Mourigal

Abstract

Rare-earth van der Waals magnets provide a route to combining strong spin-orbit coupling, large magnetic moments, and reduced dimensionality in bulk crystals. We report a comparative study of the dysprosium oxy halides DyOX (X = Cl, Br, I), which realize square-bilayer networks of Dy3+ moments separated by a tun able van der Waals gap. Structural refinements show that increasing the halide ionic radius strongly expands the inter-bilayer spacing while leaving the local bilayer geometry nearly unchanged. Magnetization and heat capacity measurements reveal two low-temperature anomalies in all three compounds: antiferromagnetic order at TN ≃ 7–10 Kandabroader anomaly near TQ ≃ 27–30 K. Single-crystal magnetization on DyOCl and Dy OBr establishes a strong hard-c-axis anisotropy, consistent with crystal-field analysis of DyOCl, which yields an XY-like ground-state g tensor.. Neutron diffraction shows long-range antiferromagnetic order in DyOCl, whereas DyOBr and DyOI exhibit sharp magnetic scattering coexisting with Warren-like diffuse features, con sistent with robust in-plane correlations and imperfect inter-bilayer registry. Inelastic neutron scattering on Dy OCl identifies crystal-field excitations near 25–30 meV and an additional magnetic mode near 10 meV whose temperature dependence is tied to the high-temperature anomaly. Taken together, these results establish DyOX as a tunable family of quasi-two-dimensional rare-earth magnets and point to candidate multipolar physics asso ciated with low-lying crystal-field states. Direct probes of quadrupolar order, such as resonant x-ray scattering or elastic-constant measurements, will be required to determine the order parameter at TQ.

Citation

Physical Review B

Pub Type

Journals

Keywords

antiferromagnet, 2-dimensional, magnetic excitations

Citation

Brooks, F. , Bai, X. , Bacsa, J. , Stone, M. , Calder, S. , Butch, N. , Garlea, V. and Mourigal, M. (2026), Tunable inter-bilayer magnetic correlations and candidate multipolar physics in the van der Waals oxyhalides DyOCl, DyOBr, and DyOI, Physical Review B (Accessed September 9, 2026)

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