{
  "abstract": "Thin-film Mn$_5$Si$_3$ is a prominent altermagnetic candidate owing to its metallicity, demonstrated anisotropic anomalous transport, and proposed $d$-wave exchange splitting that could enable spin-polarized transport. Its postulated altermagnetic structure has zero propagation vector, unlike the bulk collinear antiferromagnetic AFM2 phase, which orders at the $M$ star. We analyze both phases using Landau theory, first-principles paramagnetic-instability calculations, and Monte Carlo simulations. AFM2 appears in Landau theory as a symmetry-protected inversion-even, permutation-odd mode at a single arm of the $M$ star. At $Γ$, the same intracell pattern belongs to the collinear sector of an $E_{2g}$ order parameter; both phases require higher-order terms for their selection. Disordered-local-moment calculations identify the leading exchange instability at $M$, and the resulting classical Heisenberg model orders at the bulk experimental temperature scale into the orthogonal $3M$ phase favored by single-site entropy. Magnetostructural coupling to $E_{2g}$ deformations favors single-$M$ AFM2 ordering. The estimated homogeneous-strain contribution to the relevant quartic coefficient is about a quarter of the competing entropic term near the bulk transition, while internal $E_{2g}$ relaxations are expected to provide additional stabilization. The $Γ$-point $E_{2g}$ mode, whose Landau theory contains the altermagnetic sector, is substantially weaker and further suppressed by epitaxial strain comparable to that reported for Mn$_5$Si$_3$/Si(111) films exhibiting anomalous transport. The same strain reduces the leading magnetic exchange scale. These results explain the bulk $M$-point instability but strongly disfavor relocating the propagation vector from $M$ to $Γ$ in a moderately strained bulklike Mn$_5$Si$_3$ film, leaving the identity of the Hall-active phase unresolved.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2608.13483",
  "author_total": 1,
  "authors": [
    {
      "name": "K. D. Belashchenko"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/evb38pby4c4r2.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.13483",
  "fulltext_url": null,
  "id": "evb38pby4c4r2",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.13483",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mtrl-sci"
    ],
    [
      "openalex",
      "3107|Magnetic properties of thin films"
    ]
  ],
  "openalex": "W7203480696",
  "pdf_url": "https://arxiv.org/pdf/2608.13483",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-16",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/evb38pby4c4r2.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:30:32Z",
      "native_id": "2608.13483",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.13483"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Landau theory and exchange instabilities in Mn$_5$Si$_3$: A case against strain-induced altermagnetism",
  "title_text": "Landau theory and exchange instabilities in Mn_5Si_3: A case against strain-induced altermagnetism",
  "type": "preprint",
  "updated_at": "2026-10-30T12:33:28Z",
  "url": "https://research.draconitic.com/paper/evb38pby4c4r2",
  "venue": "arXiv",
  "versions": []
}