Strong Magnetic Exchange and Frustrated Ferrimagnetic Order in a Weberite-Type InorganicOrganic Hybrid Fluoride

Clark, LM ORCID: 0000-0002-6223-3622, Albino, Marjorie, Pimenta, Vanessa, Lhoste, Jerome, da Silva, Ivan, Payen, Christophe, Grenèche, Jean-Marc, Maisonneuve, Vincent, Lightfoot, Philip and Leblanc, Marc
(2019) Strong Magnetic Exchange and Frustrated Ferrimagnetic Order in a Weberite-Type InorganicOrganic Hybrid Fluoride. Philosophical Transactions of the Royal Society A. Mathematical, Physical and Engineering Sciences, 377 (2149). 20180224-.

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We combine powder neutron diffraction, magnetometry and <sup>57</sup>Fe Mössbauer spectrometry to determine the nuclear and magnetic structures of a strongly interacting weberite-type inorganic-organic hybrid fluoride, Fe<sub>2</sub>F<sub>5</sub>(H taz). In this structure, Fe<sup>2+</sup> and Fe<sup>3+</sup> cations form magnetically frustrated hexagonal tungsten bronze layers of corner-sharing octahedra. Our powder neutron diffraction data reveal that, unlike its purely inorganic fluoride weberite counterparts which adopt a centrosymmetric Imma structure, the room-temperature nuclear structure of Fe<sub>2</sub>F<sub>5</sub>(H taz) is best described by a non-centrosymmetric Ima2 model with refined lattice parameters a = 9.1467(2) Å, b = 9.4641(2) Å and c = 7.4829(2) Å. Magnetic susceptibility and magnetization measurements reveal that strong antiferromagnetic exchange interactions prevail in Fe<sub>2</sub>F<sub>5</sub>(H taz) leading to a magnetic ordering transition at T<sub>N</sub> = 93 K. Analysis of low-temperature powder neutron diffraction data indicates that below T<sub>N</sub>, the Fe<sup>2+</sup> sublattice is ferromagnetic, with a moment of 4.1(1) µ<sub>B</sub> per Fe<sup>2+</sup> at 2 K, but that an antiferromagnetic component of 0.6(3) µ<sub>B</sub> cants the main ferromagnetic component of Fe<sup>3+</sup>, which aligns antiferromagnetically to the Fe<sup>2+</sup> sublattice. The zero-field and in-field Mössbauer spectra give clear evidence of an excess of high-spin Fe<sup>3+</sup> species within the structure and a non-collinear magnetic structure. This article is part of the theme issue 'Mineralomimesis: natural and synthetic frameworks in science and technology'.

Item Type: Article
Uncontrolled Keywords: coordination frameworks, fluorides, neutron diffraction, Fe-57 Mossbauer spectrometry
Depositing User: Symplectic Admin
Date Deposited: 30 May 2019 10:28
Last Modified: 19 Jan 2023 00:43
DOI: 10.1098/rsta.2018.0224
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