Magnon band splitting without altermagnetism in CuF2
Abstract
Conclusive identification of an altermagnetic state requires going beyond mere symmetry arguments. We illustrate this in a combined computational and experimental study of the rutile-like material CuF2, which is on the list of predicted altermagnets. Using ab initio and linear spin-wave calculations supplied by magnetization measurements, we show that CuF2 in its experimental monoclinic structure can be described by a spin-1/2 model of weakly coupled square-lattice layers with the in-plane coupling J1≃ 115 K and two synergistic antiferromagnetic interplane couplings amounting to 4% and 8% of J1, respectively. Driven by long-range superexchange, these interlayer couplings are oblique to the square planes, resulting in the unit-cell doubling in the magnetically ordered state, thus effectively suppressing any altermagnetic band splitting. Concurrently, we identify unusually strong Dzyaloshinskii-Moriya interactions, |D|/J1≃ 0.3, that produce spin canting and, together with order-by-disorder effect, pin the Néel vector to the crystallographic b-axis. Additionally, DM anisotropy promotes magnon band splitting, but these bands remain non-chiral. Our results highlight the importance of relativistic effects even in 3d magnets with altermagnetic symmetries.
Related
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BibTeX
@misc{rousochatzakis2026magnon,
title = {{Magnon band splitting without altermagnetism in CuF2}},
author = {Ioannis Rousochatzakis and Oleg Janson and Alexander A. Tsirlin},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.11838},
eprint = {2610.11838},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.11838},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Magnon band splitting without altermagnetism in CuF2
AU - Ioannis Rousochatzakis
AU - Oleg Janson
AU - Alexander A. Tsirlin
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.11838
UR - https://arxiv.org/abs/2610.11838
AB - Conclusive identification of an altermagnetic state requires going beyond mere symmetry arguments. We illustrate this in a combined computational and experimental study of the rutile-like material CuF_2, which is on the list of predicted altermagnets. Using ab initio and linear spin-wave calculations supplied by magnetization measurements, we show that CuF_2 in its experimental monoclinic structure can be described by a spin-1/2 model of weakly coupled square-lattice layers with the in-plane coupling J_1≃ 115 K and two synergistic antiferromagnetic interplane couplings amounting to 4% and 8% of J_1, respectively. Driven by long-range superexchange, these interlayer couplings are oblique to the square planes, resulting in the unit-cell doubling in the magnetically ordered state, thus effectively suppressing any altermagnetic band splitting. Concurrently, we identify unusually strong Dzyaloshinskii-Moriya interactions, |D|/J_1≃ 0.3, that produce spin canting and, together with order-by-disorder effect, pin the Néel vector to the crystallographic b-axis. Additionally, DM anisotropy promotes magnon band splitting, but these bands remain non-chiral. Our results highlight the importance of relativistic effects even in 3d magnets with altermagnetic symmetries.
ER -