title: Pressure-induced spin-state transition in BiCoO3.
abstract: The structural and electronic properties of BiCoO(3) under high pressure have been investigated. Synchrotron X-ray and neutron powder diffraction studies show that the structure changes from a polar PbTiO(3) type to a centrosymmetric GdFeO(3) type above 3 GPa with a large volume decrease of 13% at room temperature revealing a spin-state change. The first-order transition is accompanied by a drop of electrical resistivity. Structural results show that Co(3+) is present in the low spin state at high pressures, but X-ray emission spectra suggest that the intermediate spin state is present. The pressure-temperature phase diagram of BiCoO(3) has been constructed enabling the transition temperature at ambient pressure to be estimated as 800-900 K.
authors.affiliation: Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan. oka@issp.u-tokyo.ac.jp
authors.forename: Kengo
authors.initials: K
authors.lastname: Oka
authors.forename: Masaki
authors.initials: M
authors.lastname: Azuma
authors.forename: Wei-tin
authors.initials: WT
authors.lastname: Chen
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yusa
authors.forename: Alexei A
authors.initials: AA
authors.lastname: Belik
authors.forename: Eiji
authors.initials: E
authors.lastname: Takayama-Muromachi
authors.forename: Masaichiro
authors.initials: M
authors.lastname: Mizumaki
authors.forename: Naoki
authors.initials: N
authors.lastname: Ishimatsu
authors.forename: Nozomu
authors.initials: N
authors.lastname: Hiraoka
authors.forename: Masahiko
authors.initials: M
authors.lastname: Tsujimoto
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Tucker
authors.forename: J Paul
authors.initials: JP
authors.lastname: Attfield
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Shimakawa