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15 February 2016

High Pressure Synthesis of the Cation‐ordered Perovskite 3C1: 2‐Ba3NaRu2O9

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,…
15 February 2016

Control of L-type ferrimagnetism by the Ce/vacancy ordering in the A-site-ordered perovskite Ce1/2Cu3Ti4O12

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-type…
15 February 2016

Hard–soft synthesis of a new series of vacancy-ordered perovskites, CaCrO 3− δ

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 a…
15 February 2016

Nonmagnetic spin-singlet dimer formation and coupling to the lattice in the 6H perovskite Ba3CaRu2O9

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 display…
15 February 2016

The verwey phase of magnetite—a long-running mystery in magnetism

MS Senn, JP Wright, JP Attfield, Journal of the Korean Physical Society 62 (2013), 1372-1375 Magnetite (Fe3O4) is the original magnetic material and the parent of ferrite magnets, with modern applications ranging from spintronics to MRI contrast agents. At ambient temperatures magnetite has a cubic spinel-type crystal structure, but it undergoes a complex structural distortion…
15 February 2016

Valence Change of A′-Site Mn by A-Site Doping in La1–x Na x Mn3Ti4O12

Takenori Tohyama, Mark S. Senn, Takashi Saito, Wei-tin Chen, Chiu C. Tang, J. Paul Attfield, and Yuichi Shimakawa. Chem. Mater.,25 (2013), 178–183 A-site-ordered perovskites La1–xNaxMn3Ti4O12 with (x = 0, 0.5, 1) were synthesized under high-pressure and high-temperature conditions, and their crystal structures and magnetic properties were investigated. Ti/Mn occupancies at the B site were also…
15 February 2016

“Hard–Soft” Synthesis of SrCrO3− δ Superstructure Phases

Hard-soft synthesis of SrCrO3-δ superstructure phases. Angel M. Arévalo-López, Jennifer A. Rodgers, Mark S. Senn, Falak Sher, James Farnham, William Gibbs, and J. Paul Attfield. Angew. Chem. Int. Ed. 124 (2012) 10949 “Soft” reactions, which alter local chemistry and structure while retaining the basic lattice arrangement, are important for synthesizing solids with novel properties. For…
15 February 2016

Charge Order at the Frontier between the Molecular and Solid States in Ba3NaRu2O9

Simon A. J. Kimber, Mark S. Senn, Simone Fratini, Hua Wu, Adrian H. Hill, Pascal Manuel, J. Paul Attfield, Dimitri N. Argyriou, and Paul. F. Henry, Physical Review Letters 108 (2012), 217205 We show that the valence electrons of Ba 3 NaRu 2 O 9 , which has a quasimolecular structure, completely crystallize below 210 K. Using an extended Hubbard model,…
15 February 2016

Electronic orders in the Verwey structure of magnetite

Mark S. Senn, Ingo Loa, Jon P. Wright, and J. Paul Attfield, Phys. Rev. B 85 (2012), 125119 Electronic structure calculations of the Verwey ground state of magnetite, Fe 3 O 4 , using density functional theory with treatment of on-site Coulomb interactions (DFT+U scheme), are reported. These calculations use the recently published experimental crystal structure coordinates…
15 February 2016

Charge order and three-site distortions in the Verwey structure of magnetite

MS Senn, JP Wright, JP Attfield, Nature 481 (2012), 173-176 The mineral magnetite (Fe3O4) undergoes a complex structural distortion and becomes electrically insulating at temperatures less than 125 kelvin. Verwey proposed in 1939 that this transition is driven by a charge ordering of Fe2+ and Fe3+ ions, but the ground state of the low-temperature phase…