Second-harmonic signal in electric-field-modulated EPR spectra of Fe3 spin triangles

Jason S. R. McCoombs; Jorge I. Hilari; Jérôme Robert; Balwant Singh Chauhan; Ratnamala Chatterjee; Filippo Troiani; Athanassios K. Boudalis

Second-harmonic signal in electric-field-modulated EPR spectra of Fe3 spin triangles

Materials Science 2026-07-08 v1 Quantum Physics

Authors: Jason S. R. McCoombs , Jorge I. Hilari , Jérôme Robert , Balwant Singh Chauhan , Ratnamala Chatterjee , Filippo Troiani , Athanassios K. Boudalis

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Abstract

We present electric-field-modulated electron paramagnetic resonance (EFM-EPR) measurements on centrosymmetric single crystals of the molecular spin triangle $\mathrm{[{Fe_3}O({O_2}CPh){_6}(py){_3}]ClO{_4}{\cdot}py}$ ( $\bf{Fe_3}$ ). We provide the first observation of second harmonic EFM-EPR signal in polynuclear magnetic molecules. This signal is simulated and explained in terms of an electric-field induced modulation of the isotropic exchange in the molecule, and of their symmetry lowering resulting from a Jahn-Teller effect. Additionally, an unexpected first harmonic EFM-EPR signal is observed. Various plausible symmetry-breaking mechanisms are discussed in an attempt to explain this feature, whose observation is unexpected in a nominally centrosymmetric crystal.

Keywords

electron paramagnetic resonance electric-field modulation molecular spin triangles Jahn-Teller effect second harmonic generation exchange interaction

Cite

@article{arxiv.2607.07747,
  title  = {Second-harmonic signal in electric-field-modulated EPR spectra of Fe3 spin triangles},
  author = {Jason S. R. McCoombs and Jorge I. Hilari and Jérôme Robert and Balwant Singh Chauhan and Ratnamala Chatterjee and Filippo Troiani and Athanassios K. Boudalis},
  journal= {arXiv preprint arXiv:2607.07747},
  year   = {2026}
}