title: X-ray absorption and neutron diffraction studies of (Sr(1 - x)Ce(x))MnO3: transition from coherent to incoherent static Jahn-Teller distortions.
abstract: We have carried out Ce L- and Mn K-edge x-ray absorption near edge structure (XANES) measurements to experimentally determine the oxidation states of both Ce and Mn in (Sr(1 - x)Ce(x))MnO(3) (x = 0.1-0.4). It was found that although Ce is predominantly 4 + at low doping levels (x = 0.1 and 0.15), the Ce valency decreases with increasing Ce doping (reaching a value of around 3.5 + at x = 0.4). The average Mn oxidation state decreases with the increase of Ce content, with the percentage of Jahn-Teller active Mn(3+) ions increasing from 26% (x = 0.1) to 57% (x = 0.4). Precise structural parameters were also obtained from high resolution neutron diffraction studies for samples with x = 0.1-0.3. The crystal structure remains tetragonal in I4/mcm for x ≤ 0.3. The octahedral tilt angle increases with increasing Ce content, but the distortion of the MnO(6) octahedra is reduced significantly at x ≥ 0.2 due to a transition from long-range ordered Jahn-Teller distortions to incoherent static distortions.
authors.affiliation: Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW, Australia. zhaoming.zhang@ansto.gov.au
authors.forename: Zhaoming
authors.initials: Z
authors.lastname: Zhang
authors.forename: Brendan J
authors.initials: BJ
authors.lastname: Kennedy
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Howard
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Jang
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Knight
authors.forename: Motohide
authors.initials: M
authors.lastname: Matsuda
authors.forename: Michihiro
authors.initials: M
authors.lastname: Miyake