{
  "abstract": "Cryptomelane is a hollandite-like material consisting of K⁺ cations in an α-MnO₂ tunnel-like crystallographic motif. Cryptomelane with stoichiometry K x Mn₈O₁₆ (x ≈ 1.45) has been synthesized and its magnetic properties investigated using variable-temperature magnetic susceptibility, heat capacity, and neutron powder diffraction. Three distinct transitions at T ₁ = 184 K, T ₂ = 54.5 K, and T ₃ = 24 K are observed. At T ₁ there is a subtle tetragonal → monoclinic transition associated with emergence of a set of nonmagnetic superstructure peaks indexable to a k⃗struc≈0.74c*⃗ incommensurate modulation parallel to the α-MnO₂ tunnels. Our findings are consistent with a relation previously reported in titanate hollandites, that x≈2|k⃗struc| . Magnetic Bragg peaks emerge below T ₂ = 54.5 K, and their positions indicate an incommensurate modulated magnetic structure. The model consistent with the data is a dual- k⃗mag structure with a ferromagnetic |k⃗mag|=0 component and an incommensurate k⃗mag≈0.37c*⃗ , with the latter most likely to be helical. The period of oscillation of the incommensurate magnetic component is in line with predictions based on a Heisenberg spin Hamiltonian [Mandal et al. Phys. Rev. B 2014, 90, 104420]. Below T ₃ = 24 K, there is a magnetic transition, which gives rise to a different set of magnetic Bragg peaks indicative of a highly complex magnetic structure.",
  "abstract_shown": true,
  "affiliations": [
    "Cavendish Laboratory, University of Cambridge, Cambridge CB3 0US, U.K.",
    "Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, U.K.",
    "Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.",
    "Faraday Materials Laboratory (FaMaL), Materials Research Centre, Indian Institute of Science, C. V. Raman Avenue, Bangalore 560012, India.",
    "Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20156, Cedex 9, Grenoble 38042, France.",
    "Diamond Light Source, Ltd., Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, U.K."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 12,
  "authors": [
    {
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        0,
        1,
        2
      ],
      "name": "Liam A V Nagle-Cocco",
      "orcid": "0000-0001-9265-1588"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Joshua D Bocarsly",
      "orcid": "0000-0002-7523-152X"
    },
    {
      "affs": [
        3,
        0
      ],
      "name": "Krishnakanth Sada"
    },
    {
      "affs": [
        0
      ],
      "name": "Nicola D Kelly",
      "orcid": "0000-0003-2861-1623"
    },
    {
      "affs": [
        2
      ],
      "name": "Mathias A Kiefer"
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    {
      "affs": [
        4
      ],
      "name": "Emmanuelle Suard",
      "orcid": "0000-0001-5966-5929"
    },
    {
      "affs": [
        5
      ],
      "name": "Sarah J Day"
    },
    {
      "affs": [
        0
      ],
      "name": "Cheng Liu",
      "orcid": "0000-0002-3509-951X"
    },
    {
      "affs": [
        1
      ],
      "name": "Clare P Grey",
      "orcid": "0000-0001-5572-192X"
    },
    {
      "affs": [
        3
      ],
      "name": "Prabeer Barpanda",
      "orcid": "0000-0003-0902-3690"
    },
    {
      "affs": [
        4
      ],
      "name": "Clemens Ritter",
      "orcid": "0000-0003-3674-3378"
    },
    {
      "affs": [
        0
      ],
      "name": "Siân E Dutton",
      "orcid": "0000-0003-0984-5504"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7etqg8aj3068t.bib",
  "cited_by": 0,
  "doi": "10.1021/acs.chemmater.6c01980",
  "fulltext_url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13718541/?tool=EBI",
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  "language": "eng",
  "licence": "CC-BY",
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      "3104|Advanced Condensed Matter Physics"
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  "pdf_url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13718541/pdf/?tool=EBI",
  "pmcid": "PMC13718541",
  "pmid": "42959894",
  "published": "2026-10-06",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7etqg8aj3068t.ris",
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      "first_seen": "2026-10-31T00:20:37Z",
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      "field": "physics",
      "origin": "openalex:3104|Advanced Condensed Matter Physics",
      "subfield": "condensed-matter"
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  ],
  "title": "Incommensurate Structural and Magnetic Modulations in Potassium-Rich Cryptomelane, KxMn8O16 (x ≈ 1.45)",
  "title_text": "Incommensurate Structural and Magnetic Modulations in Potassium-Rich Cryptomelane, KxMn8O16 (x ≈ 1.45)",
  "type": "peer-reviewed",
  "updated_at": "2026-11-02T12:22:33Z",
  "url": "https://research.draconitic.com/paper/7etqg8aj3068t",
  "venue": "Chemistry of materials : a publication of the American Chemical Society",
  "versions": []
}