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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

Wei-tin Chen, Masaichiro Mizumaki, Hayato Seki,Mark S. Senn, Takashi Saito, Daisuke Kan, J. Paul Attfield & Yuichi Shimakawa, Nature Communications 5 (2014), 3909. Strong correlation between spins and conduction electrons is key in spintronic materials and devices. A few ferro- or ferrimagnetic transition metal oxides such as La1−xSrxMnO3, Fe3O4, CrO2 and Sr2FeMoO6 have spin-polarized conductionRead more

Angel M. Arevalo-Lopez, Mark S. Senn, Lauren Skedd and J. Paul Attfield, Zeitschrift für anorganische und allgemeine Chemie, 640 (2014), 1164–1167. The new phase 3C1:2-Ba3NaRu2O9 was synthesized by heating the hexagonal perovskite 6H-Ba3NaRu2O9 at 900 °C under a pressure of 9 GPa. 3C1:2-Ba3NaRu2O9 adopts the 1:2 B site-ordered cubic perovskite type structure [space group Pm1,Read more

Takashi Saito, Ryuta Yamada Clemens Ritter Mark S. Senn, J. Paul Attfield, and Yuichi Shimakawa, Inorg. Chem., 53 (2014), 1578–1584. A-site-ordered perovskite Ce1/2Cu3Ti4O12 crystallizes in two different forms, one with random and the other with ordered Ce/vacancy distribution at the A site of the prototype AA′ 3 B 4O12 structure. Both phases form a G-typeRead more

Angel M. Arevalo-Lopez, Bing Liang, Mark S. Senn, Claire Murray, Chiu Tang and J. Paul Attfield, J. Mater. Chem. C, 2 (2014), 9364-9367. New CaCrO3d superstructure phases (d ¼ 0.33, 0.4, and 0.5) have been discovered through ‘soft’ low temperature reduction of the perovskite CaCrO3 made at ‘hard’ high pressure–temperature conditions. Their structures form aRead more

Mark S Senn, Angel M Arevalo-Lopez, Takashi Saito, Yuichi Shimakawa and J Paul Attfield, Journal of Physics: Condensed Matter, 25 (2013),6. Non-conservation of magnetic neutron scattering from the six-layer hexagonal perovskite Ba3CaRu2O9 on cooling reveals that (Ru5+)2 dimers form nonmagnetic spin-singlet ground states. This is in contrast to Ba3BRu2O9 (B=Co or Ni) analogues which displayRead more