Coupled sawtooth chain exchange network in olivine Mn$_2$GeO$_4$

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Main Authors: Morano, Vincent C., Maesen, Zeno, Nikitin, Stanislav, White, Jonathan S., Honda, Takashi, Kimura, Tsuyoshi, Kenzelmann, Michel, Pajerowski, Daniel, Zaharko, Oksana
Format: Preprint
Published: 2026
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author Morano, Vincent C.
Maesen, Zeno
Nikitin, Stanislav
White, Jonathan S.
Honda, Takashi
Kimura, Tsuyoshi
Kenzelmann, Michel
Pajerowski, Daniel
Zaharko, Oksana
author_facet Morano, Vincent C.
Maesen, Zeno
Nikitin, Stanislav
White, Jonathan S.
Honda, Takashi
Kimura, Tsuyoshi
Kenzelmann, Michel
Pajerowski, Daniel
Zaharko, Oksana
contents Sawtooth chain magnets have been a subject of historical interest in the field of frustrated magnetism, with classical olivine family $M_2TX_4$, ($M$ - 3d, $T$ - 4p, $X$ - chalcogen elements) typically realizing simple $\mathbf{k} = (000)$ states. The magnetism of the Mn$_2$GeO$_4$ olivine is surprisingly complex, proceeding from commensurate states to a multiferroic commensurate + incommensurate phase. Here we report inelastic neutron scattering results from a Mn$_2$GeO$_4$ single crystal and develop an effective Hamiltonian including long-distance bilinear and dipolar interactions. The magnetic interactions are predominantly antiferromagnetic and span a three-dimensional exchange network consisting of coupled sawtooth chains. Based on the determined strength of the couplings, the dominant sawtooth chains appear at third- and fourth- rather than next-nearest-neighbor. However the next-nearest-neighbor interaction is, along with a modest Dzyaloshinskii-Moriya interaction, important for modeling the observed incommensurability. We use the best-fit Hamiltonian as the basis for Langevin dynamics simulations and Luttinger-Tisza calculations of the high-temperature commensurate transition.
format Preprint
id arxiv_https___arxiv_org_abs_2601_04908
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Coupled sawtooth chain exchange network in olivine Mn$_2$GeO$_4$
Morano, Vincent C.
Maesen, Zeno
Nikitin, Stanislav
White, Jonathan S.
Honda, Takashi
Kimura, Tsuyoshi
Kenzelmann, Michel
Pajerowski, Daniel
Zaharko, Oksana
Strongly Correlated Electrons
Sawtooth chain magnets have been a subject of historical interest in the field of frustrated magnetism, with classical olivine family $M_2TX_4$, ($M$ - 3d, $T$ - 4p, $X$ - chalcogen elements) typically realizing simple $\mathbf{k} = (000)$ states. The magnetism of the Mn$_2$GeO$_4$ olivine is surprisingly complex, proceeding from commensurate states to a multiferroic commensurate + incommensurate phase. Here we report inelastic neutron scattering results from a Mn$_2$GeO$_4$ single crystal and develop an effective Hamiltonian including long-distance bilinear and dipolar interactions. The magnetic interactions are predominantly antiferromagnetic and span a three-dimensional exchange network consisting of coupled sawtooth chains. Based on the determined strength of the couplings, the dominant sawtooth chains appear at third- and fourth- rather than next-nearest-neighbor. However the next-nearest-neighbor interaction is, along with a modest Dzyaloshinskii-Moriya interaction, important for modeling the observed incommensurability. We use the best-fit Hamiltonian as the basis for Langevin dynamics simulations and Luttinger-Tisza calculations of the high-temperature commensurate transition.
title Coupled sawtooth chain exchange network in olivine Mn$_2$GeO$_4$
topic Strongly Correlated Electrons
url https://arxiv.org/abs/2601.04908