{
  "abstract": "The well-established homometallic metallacrown Cu(II)[12-MC$_\\text{Cu(II)N(Shi)}$-4]$^{2-}$, comprising four square-planarly arranged Cu(II) ions surrounding a slightly off-plane central Cu(II) ion, provides an excellent platform for investigating magnetism in exchange-coupled Cu(II) clusters both by experimental and ab initio numerical methods. In the present work, sterically bulky substituents are introduced into the salicylhydroxamate ligand to obtain a modified derivative, Cu$({\\mathrm{II})}$[12-MC$_\\text{Cu$({\\mathrm{II})}$N(L)}$-4]$^{2-}$ (Cu$_4$Cu), thereby effectively suppressing intermolecular magnetic interactions and enabling a detailed investigation of its intrinsic ground-state spin structure and exchange interactions. Static magnetization reveals competing antiferromagnetic exchange interactions of $J_1=-8.1(2)$ THz ($-33.5(8)$ meV) between the central and the peripheral sites and $J_2=-4.40(12)$ THz ($-18.2(5)$ meV) between neighboring sites on the ring of the metallacrown, which are corroborated by ab initio broken symmetry-based density functional theory (DFT). These couplings yield an $S=1/2$ ground state for Cu$_4$Cu at low temperatures, for which X-band and high-frequency/high-field electron paramagnetic resonance (EPR) precisely determine the $g$-factors $g_x = 2.028$, $g_y = 2.056$, and $g_z = 2.222$ close to axial anisotropy and in agreement with our DFT results. The ground-state spin-configuration is characterized by $d_{xy}$-character of the unoccupied states. Furthermore, our magnetization data evidence thermal transitions across a doublet-to-quartet gap of $Δ_{1/2\\rightarrow3/2} = 4.8(4)$ THz which is also indicated by the emergence of an excited-state EPR signal.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.38989",
  "author_total": 10,
  "authors": [
    {
      "name": "Luca Bischof"
    },
    {
      "name": "Ariyan Tavakoli"
    },
    {
      "name": "Sascha Pietruska"
    },
    {
      "name": "Lena Spillecke"
    },
    {
      "name": "Ina Heckelmann"
    },
    {
      "name": "Changhyun Koo"
    },
    {
      "name": "Luca M. Carrella"
    },
    {
      "name": "Eva Rentschler"
    },
    {
      "name": "Hans Christian Schneider"
    },
    {
      "name": "Rüdiger Klingeler"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/71kawqwme8rra.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.38989",
  "fulltext_url": null,
  "id": "71kawqwme8rra",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.38989",
  "language": null,
  "licence": "CC-BY-NC-ND-4.0",
  "licence_label": "CC BY-NC-ND 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mtrl-sci"
    ],
    [
      "arxiv",
      "cond-mat.str-el"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.38989",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-28",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/71kawqwme8rra.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:23Z",
      "native_id": "2610.38989",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.38989"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Magnetism in a homometallic square-planar Cu$({\\mathrm{II})}$$_4$Cu$({\\mathrm{II})}$ metallacrown",
  "title_text": "Magnetism in a homometallic square-planar Cu(II)_4Cu(II) metallacrown",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:45Z",
  "url": "https://research.draconitic.com/paper/71kawqwme8rra",
  "venue": "arXiv",
  "versions": []
}