Field-amplified readouts of weak altermagnetic exchange in MnF2
Abstract
MnF2, the textbook two-sublattice antiferromagnet, has reemerged as a prototypical altermagnet, yet the sublattice-odd exchange that defines this identity remains under active debate: it enters the magnon splitting only in quadrature with the dipole--dipole interaction, its magnitude suppressed and its sign erased. An overdetermined first-principles total-energy mapping resolves this scale as a seventh-neighbor imbalance δJ7≃+8 μeV. The resulting Hamiltonian, with the dipole--dipole interaction included explicitly, reproduces the low-energy gap and the visible finite-momentum splitting. A longitudinal field B∥ c then acts as a linear amplifier of the hidden scale, opening two signed, field-linear readouts. The first is the compensation field B∗(Q), the position of minimum splitting, which is equal and opposite at the rotation-related partner momenta: a shift from zero field is itself evidence of a finite imbalance, its side gives the sign, and its magnitude, |B∗|≃0.34~T here, gives the scale. The second is the fixed-field contrast of the partner splittings, ≃0.14~meV at $1$~T, six times the zero-field excess: a sign check from just two spectra. Both readouts survive a $0.12$~meV energy resolution, and the construction carries over to any easy-axis collinear altermagnet, bringing μeV altermagnetic exchange within present instrumental reach.
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BibTeX
@misc{jiang2026fieldamplified,
title = {{Field-amplified readouts of weak altermagnetic exchange in MnF$_2$}},
author = {Guowen Jiang and Feilong Wang and Yunhua Wang and Fawei Zheng and Bin Xi and Hong-Gang Luo and Jize Zhao},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.26540},
eprint = {2608.26540},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.26540},
}
RIS
TY - UNPB
TI - Field-amplified readouts of weak altermagnetic exchange in MnF_2
AU - Guowen Jiang
AU - Feilong Wang
AU - Yunhua Wang
AU - Fawei Zheng
AU - Bin Xi
AU - Hong-Gang Luo
AU - Jize Zhao
PY - 2026
DA - 2026/08/28
PB - arXiv
DO - 10.48550/arxiv.2608.26540
UR - https://arxiv.org/abs/2608.26540
AB - MnF_2, the textbook two-sublattice antiferromagnet, has reemerged as a prototypical altermagnet, yet the sublattice-odd exchange that defines this identity remains under active debate: it enters the magnon splitting only in quadrature with the dipole--dipole interaction, its magnitude suppressed and its sign erased. An overdetermined first-principles total-energy mapping resolves this scale as a seventh-neighbor imbalance δJ_7≃+8 μeV. The resulting Hamiltonian, with the dipole--dipole interaction included explicitly, reproduces the low-energy gap and the visible finite-momentum splitting. A longitudinal field B∥ c then acts as a linear amplifier of the hidden scale, opening two signed, field-linear readouts. The first is the compensation field B^∗(Q), the position of minimum splitting, which is equal and opposite at the rotation-related partner momenta: a shift from zero field is itself evidence of a finite imbalance, its side gives the sign, and its magnitude, |B^∗|≃0.34~T here, gives the scale. The second is the fixed-field contrast of the partner splittings, ≃0.14~meV at $1$~T, six times the zero-field excess: a sign check from just two spectra. Both readouts survive a $0.12$~meV energy resolution, and the construction carries over to any easy-axis collinear altermagnet, bringing μeV altermagnetic exchange within present instrumental reach.
ER -