Strong magnetic exchange and frustrated ferrimagnetic order in a weberite-type inorganic-organic hybrid fluoride
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We combine powder neutron diffraction, magnetometry and 57Fe Mössbauer spectrometry to determine the nuclear and magnetic structures of a strongly interacting weberite-type inorganic-organic hybrid fluoride, Fe2F5(Htaz). In this structure, Fe2+ and Fe3+ cations form magnetically frustrated hexagonal tungsten bronze (HTB) 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 Fe2F5(Htaz) 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 magnetisation measurements reveal that strong antiferromagnetic exchange interactions prevail in Fe2F5(Htaz) leading to a magnetic ordering transition at TN = 93 K. Analysis of low-temperature powder neutron diffraction data indicates that below TN, the Fe2+ sublattice is ferromagnetic, with a moment of 4.1(1) μB per Fe2+ at 2 K, but that an antiferromagnetic component of 0.6(3) μB cants the main ferromagnetic component of Fe3+, which aligns antiferromagnetically to the Fe2+ sublattice. The zero-field and in-field Mössbauer spectra give clear evidence of an excess of high-spin Fe3+ species within the structure and a non collinear magnetic structure.
Clark , L , Pimenta , V , Lhoste , J , da Silva , I , Payen , C , Grenèche , J-M , Maisonneuve , V , Lightfoot , P & Leblanc , M 2019 , ' Strong magnetic exchange and frustrated ferrimagnetic order in a weberite-type inorganic-organic hybrid fluoride ' , Philosophical Transactions of the Royal Society. A, Mathematical, Physical and Engineering Sciences , vol. 377 , no. 2149 . https://doi.org/10.1098/rsta.2018.0224
Philosophical Transactions of the Royal Society. A, Mathematical, Physical and Engineering Sciences
Copyright © 2019 The Author(s). This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1098/rsta.2018.0224
DescriptionLC acknowledges the University of Liverpool for start-up funding and support. Work at the University of St Andrews was supported by a Leverhulme Research Project Grant. Access to beam time at the ISIS Neutron and Muon Facility was supported by the Science and Technology Facilities Council. The authors also gratefully acknowledge Delphine Toulemon, ITODYS, UMR7086 CNRS, Université Paris VII, for assistance with magnetisation measurements.
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