Wei-Tin Chen, Chin-Wei Wang, Hung-Cheng Wu, Fang-Cheng Chou, Hung-Duen Yang, Arkadiy Simonov, and Mark S. Senn, Phys. Rev. B 97, 144102 (2018) There has recently been renewed interest in improper ferroelectricity due to the discovery of a “hybrid” mechanism by which two nonpolar lattice modes couple to a third polar mode. Here, the authorsRead more
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Chris Ablitt, Sarah Craddock, Mark S. Senn, Arash A. Mostofi & Nicholas C. Bristowe, npj Computational Materials 3, Article number: 44 (2017) doi:10.1038/s41524-017-0040-0 Why is it that ABO3 perovskites generally do not exhibit negative thermal expansion (NTE) over a wide temperature range, whereas layered perovskites of the same chemical family often do? It isRead more
Sarah Craddock, Mark S. Senn. Journal of Solid State Chemistry 248 (2017) 157–163. There has been renewed interest in the Ruddlesden-Popper phase (n=2) of composition Can+1MnnO3 n+1 in the light of recent research that has highlighted the nature of the improper ferroelectric ground state, which arises due to the couplings between specific combinations of MnO6Read more
Mark S. Senn, Acta Cryst. (2017). A73, 1-3. The significance of an algorithm developed by H. T. Stokes & B. J. Campbell [Acta Cryst. (2017), A73, 4-13] is discussed. The algorithm promises to be a key tool for understanding the structure-property relationships of the many technologically important materials that display incommensurate modulations in their atomicRead more
D. G. Porter, M. S. Senn, D. D. Khalyavin, A. Cortese, N. Waterfield-Price, P. G. Radaelli, P. Manuel, H.-C. zur-Loye, C. Mazzoli, and A. Bombardi The magnetic ground state of Sr3ARuO6 , with A=(Li,Na) , is studied using neutron diffraction, resonant x-ray scattering, and laboratory characterization measurements of high-quality crystals. Combining these results allows usRead more
Ronghuan Zhang, Mark S. Senn, and Michael A. Hayward, Chem. Mater., DOI: 10.1021/acs.chemmater.6b03931 The cooperative tilting distortions of n = 2 Ruddlesden–Popper oxides can be utilized to break the inversion symmetry of the host lattice and induce ferroelectric behavior. Unfortunately the desired a–a–c+/a–a–c+ structural deformation is only stabilized in phases with extremely small structuralRead more
M. S. Senn, D. A. Keen, T. C. A. Lucas, J. A. Hriljac, and A. L. Goodwin, Phys. Rev. Lett. 116 (2016), 207602. By using a symmetry motivated basis to evaluate local distortions against pair distribution function data (PDF), we show without prior bias, that the off-centre Ti displacements in the archetypal ferroelectric BaTiO3 are zone centred and rhombohedral-like in natureRead more
Mark S. Senn, Claire A. Murray, Xuan Luo, Lihai Wang, Fei-Ting Huang, Sang-Wook Cheong, Alessandro Bombardi, Chris Ablitt, Arash A. Mostofi, and Nicholas C. Bristowe, J. Am. Chem. Soc., 10.1021/jacs.5b13192 The layered perovskite Ca3–xSrxMn2O7 is shown to exhibit a switching from a material exhibiting uniaxial negative to positive thermal expansion as a function of x.Read more
Mark S. Senn, Jon P. Wright, James Cumby, and J. Paul Attfield, Phys. Rev. B 92 (2015), 024104. The thermal evolution of electronic order in the complex Verwey ground state of magnetite (Fe 3 O 4 ) has been determined through 22 high-accuracy synchrotron x-ray structure refinements using three 10–40μm grains of stoichiometric magnetite. A robust fitting function isRead more
M. S. Senn, A. Bombardi, C. A. Murray, C. Vecchini, A. Scherillo, X. Luo, and S. W. Cheong, Phys. Rev. Lett. 114 (2015), 035701. We present new results on the microscopic nature of the ferroelectricity mechanisms in Ca 3 Mn 2 O 7 and Ca 3 Ti 2 O 7 . To the first approximation, we confirm the hybrid improper ferroelectric mechanism recently proposed by Benedek and FennieRead more