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@PHDTHESIS{Alexeev:320253,
      author       = {Alexeev, Pavel},
      othercontributors = {Roehlsberger, Ralf and Nielsch, Kornelius and Hermann,
                          Raphael and Wille, Hans-Christian},
      title        = {{N}uclear {R}esonance {S}cattering {S}tudy of {I}ridates,
                      {I}ridium and {A}ntimony {B}ased {P}yrochlores},
      issn         = {1435-8085},
      school       = {Universität Hamburg},
      type         = {Dissertation},
      publisher    = {Verlag Deutsches Elektronen-Synchrotron},
      reportid     = {PUBDB-2017-01621, DESY-THESIS-2017-013},
      series       = {DESY-THESIS},
      pages        = {170},
      year         = {2017},
      note         = {Dissertation, Universität Hamburg, 2017},
      abstract     = {This thesis shows the first synchrotron-based Mössbauer
                      spectroscopy studies on iridium containing compounds and
                      first vibrational spectroscopy on Sb containing compounds
                      carried out at the P01 beamline of PETRA III. In this
                      context, two types of x-ray monochromators have been
                      developed: a monochromator for 73 keV photons with medium
                      energy resolution, and a high-resolution backscattering
                      monochromator based on a sapphire crystal. The monochromator
                      for 73 keV x-rays is the key instrument for hyperfine
                      spectroscopy on Iridium compounds, while the sapphire
                      backscattering monochromator is purposed to vibrational
                      spectroscopy on any Mössbauer resonances with the
                      transition energies in the 20-50 keV range. Additionally,
                      the signal detection for nuclear resonance scattering
                      experiments at the beamline was significantly improved
                      during this work, inspired by the high energies and low
                      lifetimes of the employed resonances. The first
                      synchrotron-based hyperfine spectroscopy on
                      Iridium-containing compounds was demonstrated by NRS on 73
                      keV resonance in $^{193}$Ir. The results can be interpreted
                      by dynamical theory of nuclear resonance scattering. In this
                      work, special emphasis is set onto the electronic and
                      magnetic properties of Ir nuclei in IrO$_2$ and in
                      Ruddlesden-Popper (RP) phases of strontium iridates
                      Sr$_{n+1}$IrnO$_{3n+1}$ (n = 0; 1). These systems are
                      well-suited for studies with x-ray scattering techniques,
                      since the scattered signal contains vast information about
                      the widely tunable crystallographic and electronic structure
                      of these systems; furthermore, studies with x-rays are less
                      limited by absorption from iridium as it is the case for
                      neutron scattering experiments. The hyperfine parameters in
                      IrO$_2$, SrIrO$_3$ and Sr$_2$IrO$_4$ have been measured via
                      Nuclear Forward Scattering for the first time. Using the
                      dynamical theory of NRS, the temperature and magnetic field
                      dependence of the electric field gradient and magnetic
                      hyperfine field on Ir nucleus have been determined for these
                      compounds. In order to broaden the perspectives of NRS with
                      the 73 keV resonance the first room temperature NRS on
                      iridium metal is carried out. The results demonstrate NRS as
                      a powerful research tool for the studies of iridium physics
                      due to the high energy of the resonant photons and the high
                      natural abundance of the $^{193}$Ir isotope under study,
                      paving the way for studies of magnetism and electronic
                      properties under extreme conditions.The second part of this
                      work is dedicated to vibrational spectroscopy with Nuclear
                      Inelastic Scattering (NIS). A sapphire backscattering
                      monochromator was designed, installed and tested at the
                      beamline. It provides high energy resolution due to the
                      sub-mK temperature control, though the resolution is limited
                      from theoretically proposed sub-meV to meV by the quality of
                      currently available sapphire crystals. With this device the
                      energy resolution of 1.3(1) meV at 23.88 keV and of 3.2(4)
                      meV at 37.13 keV was achieved. Following this development,
                      the vibrational spectra of antimony in defect pyrochlore
                      Ag-Sb-O compounds have been measured by means of NIS at
                      37.13 keV. Density of phonon states for the Sb(III) and for
                      the Sb(V) site has been revealed. The difference in
                      site-specific antimony modes illustrates the importance of
                      lattice dynamics for the engineering of these compounds.},
      cin          = {FS-PS},
      cid          = {I:(DE-H253)FS-PS-20131107},
      pnm          = {6212 - Quantum Condensed Matter: Magnetism,
                      Superconductivity (POF3-621) / 6G3 - PETRA III (POF3-622) /
                      PHGS, VH-GS-500 - PIER Helmholtz Graduate School
                      $(2015_IFV-VH-GS-500)$},
      pid          = {G:(DE-HGF)POF3-6212 / G:(DE-HGF)POF3-6G3 /
                      $G:(DE-HGF)2015_IFV-VH-GS-500$},
      experiment   = {EXP:(DE-H253)P-P01-20150101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:gbv:18-84687},
      doi          = {10.3204/PUBDB-2017-01621},
      url          = {https://bib-pubdb1.desy.de/record/320253},
}