title: {110}-Layered B-cation ordering in the anion-deficient perovskite Pb2.4Ba2.6Fe2Sc2TiO13 with the crystallographic shear structure.
abstract: A novel anion-deficient perovskite-based compound, Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13), was synthesized via the citrate-based route. This compound is an n = 5 member of the AnBnO(3n-2) homologous series with unit-cell parameters related to the perovskite subcell a(p)≈ 4.0 Å as a(p)√2 ×a(p)× 5a(p)√2. The crystal structure of Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13) consists of quasi-2D perovskite blocks with a thickness of three octahedral layers separated by the 1/2[110](1[combining macron]01)(p) crystallographic shear (CS) planes, which are parallel to the {110} plane of the perovskite subcell. The CS planes transform the corner-sharing octahedra into chains of edge-sharing distorted tetragonal pyramids. Using a combination of neutron powder diffraction, (57)Fe Mössbauer spectroscopy and atomic resolution electron energy-loss spectroscopy we demonstrate that the B-cations in Pb(2.4)Ba(2.6)Fe(2)Sc(2)TiO(13) are ordered along the {110} perovskite layers with Fe(3+) in distorted tetragonal pyramids along the CS planes, Ti(4+) preferentially in the central octahedra of the perovskite blocks and Sc(3+) in the outer octahedra of the perovskite blocks. Magnetic susceptibility and Mössbauer spectroscopy indicate a broadened magnetic transition around T(N)∼ 45 K and the onset of local magnetic fields at low temperatures. The magnetic order is probably reminiscent of that in other AnBnO(3n-2) homologues, where G-type AFM order within the perovskite blocks has been observed.
authors.affiliation: Department of Chemistry, Moscow State University, Leninskie Gory 1-3, Moscow, 119991, Russia. olegtyablikov@icr.chem.msu.ru.
authors.forename: O A
authors.initials: OA
authors.lastname: Tyablikov
authors.forename: D
authors.initials: D
authors.lastname: Batuk
authors.forename: A A
authors.initials: AA
authors.lastname: Tsirlin
authors.forename: M
authors.initials: M
authors.lastname: Batuk
authors.forename: V Yu
authors.initials: VY
authors.lastname: Verchenko
authors.forename: D S
authors.initials: DS
authors.lastname: Filimonov
authors.forename: K V
authors.initials: KV
authors.lastname: Pokholok
authors.forename: D V
authors.initials: DV
authors.lastname: Sheptyakov
authors.forename: M G
authors.initials: MG
authors.lastname: Rozova
authors.forename: J
authors.initials: J
authors.lastname: Hadermann
authors.forename: E V
authors.initials: EV
authors.lastname: Antipov
authors.forename: A M
authors.initials: AM
authors.lastname: Abakumov