Journal Article

FZJ-2025-04074

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Proton Ordering Induces a Polar Structure in the Antiferromagnetic Solid Proton Conductor $FeH_6(PO_4)_3$

Gronych, L. M. ; Kraft, M. A.FZJ* ; Hartmann, M. ; Faka, V. ; Glikman, D. ; Koers, I. ; Li, C. ; Newnham, J. ; Braunschweig, B. ; Zeier, W. (Corresponding author)FZJ* ; Martinez de Irujo-Labalde, X. (Corresponding author)

2025
ACS Publications Washington, DC

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Please use a persistent id in citations: doi:10.1021/jacs.5c10508  doi:10.34734/FZJ-2025-04074

Abstract: Materials exhibiting coexisting exploitable properties often result in especially attractive behavior from both fundamental and applied perspectives. In particular, magnetoelectric materials combining ferroelectric and magnetic properties are increasingly becoming paramount nowadays. Here, we show that $FeH_6(PO_4)_3$ exhibits proton conductivity and the coexistence of magnetic and polar structural features, suggesting that such frameworks may be of broader interest beyond the field of proton conductors. By a combination of neutron diffraction and second harmonic generation experiments, we have demonstrated that $FeH_6(PO_4)_3$ crystallizes in the polar $R3c$ space group. Inversion symmetry breaking is triggered by a polar proton ordering within the structure. In $FeH_6(PO_4)_3$, this particular cation ordering in combination with the polar displacement of the adjacent structural units results in a polar crystal structure with a calculated net polarization of approximatel $10 μC cm{^–2}$ between 10 and 300 K. Together with an antiferromagnetic state below 28 K, determined from a combination of neutron diffraction and magnetic measurements and associated with the particular $Fe^{3+}$ octahedral arrangement, the result is the coexistence of both properties. By a detailed study of this system with a full description of the crystal structure as well as the ionic and magnetic properties, we aim to spark further investigations in magnetoelectric materials existing in the solid ionic conductor phase space.

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Contributing Institute(s):

1. Helmholtz-Institut Münster Ionenleiter für Energiespeicher (IMD-4)

Research Program(s):

1. 1221 - Fundamentals and Materials (POF4-122) (POF4-122)

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