title: La2SrCr2O7: Controlling the Tilting Distortions of n = 2 Ruddlesden-Popper Phases through A-Site Cation Order.
abstract: Structural characterization by neutron diffraction, supported by magnetic, SHG, and μ(+)SR data, reveals that the n = 2 Ruddlesden-Popper phase La2SrCr2O7 adopts a highly unusual structural configuration in which the cooperative rotations of the CrO6 octahedra are out of phase in all three Cartesian directions (ΦΦΦz/ΦΦΦz; a(-)a(-)c(-)/a(-)a(-)c(-)) as described in space group A2/a. First-principles DFT calculations indicate that this unusual structural arrangement can be attributed to coupling between the La/Sr A-site distribution and the rotations of the CrO6 units, which combine to relieve the local deformations of the chromium-oxygen octahedra. This coupling suggests new chemical "handles" by which the rotational distortions or A-site cation order of Ruddlesden-Popper phases can be directed to optimize physical behavior. Low-temperature neutron diffraction data and μ(+)SR data indicate La2SrCr2O7 adopts a G-type antiferromagnetically ordered state below TN ∼ 260 K.
authors: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QR, United Kingdom.
authors: Ronghuan
authors: R
authors: Zhang
authors: School of Applied and Engineering Physics, Cornell University , Ithaca, New York 14853, United States.
authors: Brian M
authors: BM
authors: Abbett
authors: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QR, United Kingdom.
authors: Gareth
authors: G
authors: Read
authors: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors: Franz
authors: F
authors: Lang
authors: Department of Physics, Durham University , South Road, Durham DH1 3LE, United Kingdom.
authors: Tom
authors: T
authors: Lancaster
authors: Department of Chemistry, University of Houston , 112 Fleming Building, Houston, Texas 77204-5003, United States.
authors: T Thao
authors: TT
authors: Tran
authors: Department of Chemistry, University of Houston , 112 Fleming Building, Houston, Texas 77204-5003, United States.
authors: P Shiv
authors: PS
authors: Halasyamani
authors: Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors: Stephen J
authors: SJ
authors: Blundell
authors: Department of Materials Science and Engineering, Cornell University , Ithaca, New York 14853, United States.
authors: Nicole A
authors: NA
authors: Benedek
authors: Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QR, United Kingdom.
authors: Michael A
authors: MA
authors: Hayward