title: La2SrCr2O7F2: A Ruddlesden-Popper Oxyfluoride Containing Octahedrally Coordinated Cr(4+) Centers.
abstract: The low-temperature fluorination of the n = 2 Ruddlesden-Popper phase La2SrCr2O7 yields La2SrCr2O7F2 via a topochemical fluorine insertion reaction. The structure-conserving nature of the fluorination reaction means that the chromium centers of the initial oxide phase retain an octahedral coordination environment in the fluorinated product, resulting in a material containing an extended array of apex-linked Cr(4+)O6 units. Typically materials containing networks of octahedrally coordinated Cr(4+) centers can only be prepared at high pressure; thus, the preparation of La2SrCr2O7F2 demonstrates that low-temperature topochemical reactions offer an alternative synthesis route to materials of this type. Neutron diffraction, magnetization, and μ(+)SR data indicate that La2SrCr2O7F2 undergoes a transition to an antiferromagnetic state below TN ≈ 140 K. The structure-property relations of this phase and other Cr(4+) oxide phases are discussed.
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QR, United Kingdom.
authors.forename: Ronghuan
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QR, United Kingdom.
authors.forename: Gareth
authors.initials: G
authors.lastname: Read
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, U.K.
authors.forename: Franz
authors.initials: F
authors.lastname: Lang
authors.affiliation: Department of Physics, Durham University , South Road, Durham DH1 3LE, U.K.
authors.forename: Tom
authors.initials: T
authors.lastname: Lancaster
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, U.K.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Blundell
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QR, United Kingdom.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hayward