Altermagnetism and generalised tensorial properties in the exchange multiplet framework
Abstract
A representation-theoretic framework for the calculation of time-reversal-odd tensorial properties of magnetic materials based on the Bertaut--Izyumov exchange-multiplet formalism is developed. In contrast to approaches based on distinct magnetic point groups or spin groups for different orientations of the magnetic order parameter, the exchange-multiplet framework permits the order parameter to be treated as a continuous variable. It is shown that, for constant-moment collinear structures, covariance imposes a simple set of symmetry constraints on the tensor intertwiners appearing in a Landau--Lifshitz expansion. This leads to canonical intertwiner forms that factorise the magnetic and crystallographic parts of the tensor construction. Tensor fields can be built to retain a Cartesian representation in the physical variables while acquiring a systematic dependence on the order-parameter direction through symmetry-adapted polynomial bases. Magnetic-point-group selection rules are recovered automatically for arbitrary order-parameter directions, while the framework also provides a natural separation of co-rotating (SOC-free) and non-co-rotating contributions. The approach is applicable to altermagnets and conventional antiferromagnets alike and is particularly suited to experiments and first-principles calculations in which the magnetic order parameter can be continuously varied.
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BibTeX
@misc{radaelli2026altermagnetism,
title = {{Altermagnetism and generalised tensorial properties in the exchange multiplet framework}},
author = {Paolo G. Radaelli},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.28453},
eprint = {2609.28453},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.28453},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Altermagnetism and generalised tensorial properties in the exchange multiplet framework
AU - Paolo G. Radaelli
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2609.28453
UR - https://arxiv.org/abs/2609.28453
AB - A representation-theoretic framework for the calculation of time-reversal-odd tensorial properties of magnetic materials based on the Bertaut--Izyumov exchange-multiplet formalism is developed. In contrast to approaches based on distinct magnetic point groups or spin groups for different orientations of the magnetic order parameter, the exchange-multiplet framework permits the order parameter to be treated as a continuous variable. It is shown that, for constant-moment collinear structures, covariance imposes a simple set of symmetry constraints on the tensor intertwiners appearing in a Landau--Lifshitz expansion. This leads to canonical intertwiner forms that factorise the magnetic and crystallographic parts of the tensor construction. Tensor fields can be built to retain a Cartesian representation in the physical variables while acquiring a systematic dependence on the order-parameter direction through symmetry-adapted polynomial bases. Magnetic-point-group selection rules are recovered automatically for arbitrary order-parameter directions, while the framework also provides a natural separation of co-rotating (SOC-free) and non-co-rotating contributions. The approach is applicable to altermagnets and conventional antiferromagnets alike and is particularly suited to experiments and first-principles calculations in which the magnetic order parameter can be continuously varied.
ER -