% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@BOOK{Adiga:821202,
      author       = {Adiga, Shilpa},
      title        = {{C}rystal growth and scattering studies on two ferrites},
      volume       = {135},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-06440},
      isbn         = {978-3-95806-183-5},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {IV, 150 S.},
      year         = {2016},
      note         = {RWTH Aachen, Diss., 2015},
      abstract     = {$\textbf{(1) A detailed ferroelectric study of magnetite
                      (Fe$_{3}$O$_{4}$}$) Multiferroics, consisting of both
                      ferroelectric and ferromagnetic phases, have attracted
                      scientic and technological interest due possible
                      magnetoelectric coupling between thephases. Such materials
                      are very rare though, as conventional ferroelectricity
                      requires an empty d-shell, preventing the presence of
                      magnetism. Among unconventional mechanisms leading to
                      ferroelectricity, multiferroicity due to charge ordering
                      (CO) is a strong candidate for practical applications.
                      However, proven examples are very rare as of yet. The 120 K
                      Verwey transition (T$_{V}$) in magnetite, reported in 1939,
                      is the classical example for charge ordering. Despite
                      controversies regarding the existence of CO, magnetite has
                      been proposed as one of the CO-based multiferroics. Although
                      early experiments already indicated for example a
                      magnetoelectric effect, those studies were mainly focused on
                      complex low temperature structure rather than possible
                      multiferroicity. In order to study the ferroelectric
                      properties of magnetite by dielectric spectroscopy, a new
                      dielectric measurement set-up was built at the institute.
                      After an introduction and the description of experimental
                      techniques, this thesis begins with the presentation of our
                      newly built dielectric set-up and of the performed test
                      experiments to standardize measurements of the dielectric
                      constant. The Verwey transition is very sensitive to oxygen
                      stoichiometry. The oxygen stoichiometry was tuned by
                      appropriate gas mixtures of CO$_{2}$ and CO or
                      Ar(H$_{2}$)$_{4}$\%. I first investigated appropriate ratios
                      of CO$_{2}$ / Ar(H$_{2}$)$_{4}$\% at high temperature on
                      polycrystalline samples and confirmed the phase purity by
                      x-ray diffraction. Verwey transition was characterized
                      primarily by thermo-remanent magnetization and specific
                      heat. The results obtained from the basic macroscopic
                      analysis were used for the growth of high quality crystals
                      by optical floating zone method. Proposed low temperature
                      relaxor ferroelectric property of magnetite was studied by
                      neutron and high energy X-ray diffuse scattering
                      experiments. The observed weak diffuse scattering by neutron
                      diffraction, which was absent in high energy X-ray studies,
                      indicated that it is magnetic in origin. For the first time,
                      a time resolved X-ray diffraction technique has been
                      implemented to test the switchabilty of the polar structure
                      by application of an electric field in magnetite. The
                      observed change in the intensity of the Bragg reflection to
                      its Friedel mate (reflection related by inversion symmetry)
                      constitutes to the first microscopic proof of ferroic
                      behavior of classical magnetite. $\textbf{(2) Study of
                      various physical properties of oxygen deficient strontium
                      ferrite (SrFeO$_{3- \delta}$)}$. Colossal magnetoresistance
                      effect, i.e., the huge change in the electrical resistance
                      by the application of magnetic field is a key to the next
                      generation of magnetic memory devices. The oxygen deficient
                      strontium ferrite (SrFeO$_{3- \delta}$, $\delta$=0-0.5)
                      system exhibits [...]},
      cin          = {JCNS-2 / PGI-4 / JARA-FIT},
      cid          = {I:(DE-Juel1)JCNS-2-20110106 / I:(DE-Juel1)PGI-4-20110106 /
                      $I:(DE-82)080009_20140620$},
      pnm          = {144 - Controlling Collective States (POF3-144) / 524 -
                      Controlling Collective States (POF3-524) / 6212 - Quantum
                      Condensed Matter: Magnetism, Superconductivity (POF3-621) /
                      6213 - Materials and Processes for Energy and Transport
                      Technologies (POF3-621) / 6G4 - Jülich Centre for Neutron
                      Research (JCNS) (POF3-623)},
      pid          = {G:(DE-HGF)POF3-144 / G:(DE-HGF)POF3-524 /
                      G:(DE-HGF)POF3-6212 / G:(DE-HGF)POF3-6213 /
                      G:(DE-HGF)POF3-6G4},
      experiment   = {EXP:(DE-H253)P-P09-20150101 / EXP:(DE-MLZ)DNS-20140101 /
                      EXP:(DE-MLZ)SPODI-20140101},
      typ          = {PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/821202},
}