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
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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
Cation ordering in the 1322 perovskite CaCu3Fe2Nb2O12 has been investigated by synchrotron X-ray diffraction structure analysis, high-resolution electron microscopy, and magnetic measurements. All of the samples have full 1:3 ordering of Ca and Cu cations at the perovskite A-sites, but the Fe and Nb cations at the B sites show different degrees of orderingRead more
T. P. Croft, C. Lester, M. S. Senn, A. Bombardi, and S. M. Hayden, Phys. Rev. B 89 (2014), 224513 We report hard (14 keV) x-ray diffraction measurements on three compositions (x=0.11,0.12,0.13) of the high-temperature superconductor La 2−x Sr x CuO 4 . All samples show charge density wave (CDW) order with onset temperatures in the range 51–80Read more