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@PHDTHESIS{Schffmann:892131,
      author       = {Schöffmann, Patrick},
      title        = {{S}toichiometric control and magnetoelectric coupling in
                      artificial multiferroic heterostructures},
      volume       = {247},
      school       = {RWTH Aachen},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2021-01966},
      isbn         = {978-3-95806-575-8},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {vii, 176 S.},
      year         = {2021},
      note         = {Dissertation, RWTH Aachen, 2021},
      abstract     = {The demand for smaller and faster information storage
                      media, new types of sensors and multifunctional devices has
                      lead to a rush in research on transition metal oxides
                      (TMO's). Strong electronic correlations in TMO's lead to a
                      wealth of new and interesting effects. Particularly the use
                      of artificial multiferroic heterostructures using advanced
                      thin film growth techniques, has attracted a lot of
                      interest, as they enable the tailoring of the physical
                      properties of individual materials and hold the promise of
                      new combined functionality. The subject of this thesis is
                      control of the magnetisation in thin TMO films using the
                      ferroelectric substrate
                      [Pb(Mg$_{1/3}$Nb${_{2/3}}$)O$_{3}$]$_{0.7}$-[PbTiO$_{3}$]$_{0.3}$
                      (PMN-PT). The first part of this thesis is about the
                      fabrication and investigation of SrCoO$_{3-{\delta}}$, which
                      has different magnetic and conductive properties depending
                      on the oxygen content. Importantly, the antiferromagnetic,
                      insulating SrCoO$_{2.5}$ can be transformed reversibly in
                      the ferromagnetic, metallic SrCoO$_{3}$. To grow epitaxial
                      and stoichiometric Sr$_{1}$Co$_{1}$O$_{2.5}$ films by
                      molecular beam epitaxy (MBE), the deposition parameter have
                      to be precisely controlled. To determine the Co-to-Sr ratio
                      $\textit{in-situ}$ and optimise it, Reflection High Energy
                      Electron Diffraction (RHEED) can be used. The RHEED
                      scattering pattern changes depending on the Co/Sr ratio and
                      can be used to determine Co excess or deficiency and to grow
                      stoichiometric Sr$_{1}$Co$_{1}$O$_{2.5}$ samples. High
                      quality SrCoO$_{2.5}$ can be transformed to SrCoO$_{3}$ by
                      heating in oxygen flow and the resulting films remain stable
                      in vacuum. SrCoO$_{3-{\delta}}$ films (with $\delta$< 0.25)
                      form three distinct magnetic phases and show an exchange
                      bias effect. The magnetic phases are distributed uniformly
                      throughout the film, as can be determined by Polarised
                      Neutron Reflectometry (PNR). Due to a mismatch of lattice
                      constants, SrCoO$_{2.5}$ films can't be grown directly on
                      PMN-PT. However, using an La$_{0.67}$Sr$_{0.33}$MnO$_{3}$
                      buffer layer, crystalline
                      SrCoO$_{2.5}$/La$_{0.67}$Sr$_{0.33}$MnO$_{3}$/PMN-PT
                      heterostructures can be grown. The second part of the
                      dissertation is about the magnetoelectric coupling in
                      Fe$_{3}$O$_{4}$/PMN-PT(001) and Fe$_{3}$O$_{4}$/PMN-PT(011)
                      heterostructures grown by pulsed laser deposition. The
                      strain and polarisation of the substrate with applied
                      electric field mediate the coupling to the magnetisation in
                      the ferrimagnetic layer. Using a qualitative model, the
                      strength of the different contributions can be estimated.
                      The substrate cut and orientation of the sample in the
                      magnetic field has a strong influence on the magnetoelectric
                      behaviour of the layer.},
      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          = {632 - Materials – Quantum, Complex and Functional
                      Materials (POF4-632) / 6G4 - Jülich Centre for Neutron
                      Research (JCNS) (FZJ) (POF4-6G4)},
      pid          = {G:(DE-HGF)POF4-632 / G:(DE-HGF)POF4-6G4},
      experiment   = {EXP:(DE-MLZ)MARIA-20140101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/892131},
}