An electronically driven improper ferroelectric : tungsten bronzes as microstructural analogs for the hexagonal manganites
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Since the observation that the properties of ferroic domain walls (DWs) can differ significantly from the bulk materials in which they are formed, it has been realized that domain wall engineering offers exciting new opportunities for nanoelectronics and nanodevice architectures. Here, a novel improper ferroelectric, CsNbW2O9, with the hexagonal tungsten bronze structure, is reported. Powder neutron diffraction and symmetry mode analysis indicate that the improper transition (TC = 1100 K) involves unit cell tripling, reminiscent of the hexagonal rare earth manganites. However, in contrast to the manganites the symmetry breaking in CsNbW2O9 is electronically driven (i.e., purely displacive) via the second-order Jahn-Teller effect in contrast to the geometrically-driven tilt mechanism of the manganites. Nevertheless CsNbW2O9 displays the same kinds of domain microstructure as those found in the manganites, such as the characteristic six-domain "cloverleaf" vertices and DW sections with polar discontinuities. The discovery of a completely new material system, with domain patterns already known to generate interesting functionality in the manganites, is important for the emerging field of DW nanoelectronics.
McNulty , J A , Tran , T T , Halasyamani , P S , McCartan , S , MacLaren , I , Gibbs , A , Lim , F , Turner , P , Gregg , J M , Lightfoot , P & Morrison , F D 2019 , ' An electronically driven improper ferroelectric : tungsten bronzes as microstructural analogs for the hexagonal manganites ' , Advanced Materials , vol. 31 , no. 40 , 1903620 . https://doi.org/10.1002/adma.201903620
Copyright © 2019 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim. This work is 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/10.1002/adma.201903620
DescriptionJAM would like to acknowledge the School of Chemistry, University of St Andrews for the allocation of a PhD studentship through the EPSRC doctoral training grant (EP/ K503162/1). The work carried out at the University of St Andrews and Queens University Belfast was carried out as part of an EPSRC-funded collaboration (EP/P02453X/1 and EP/P024637/1). The work carried out at the University of Glasgow was carried out as part of the EPSRC-funded CDT in Photonic Integration and Advanced Data Storage (EP/L015323/1). TTT and PSH thank the Welch Foundation (Grant E-1457) and NSF (DMR-1503573) for support.
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