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@PHDTHESIS{Schmitz:283618,
      author       = {Schmitz, Markus},
      title        = {{S}train and electric field mediated manipulation of
                      magnetism in
                      {L}a($_{1-x}$){S}r$_{x}${M}n{O}$_{3}$/{B}a{T}i{O}$_{3}$
                      heterostructures},
      volume       = {129},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-01920},
      isbn         = {978-3-95806-164-4},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {VI, 141 S.},
      year         = {2016},
      note         = {RWTH Aachen, Diss., 2015},
      abstract     = {Heterostructures of ferromagnetic
                      La$_{1-x}$Sr$_{x}$MnO$_{3}$ (LSMO) and ferroelectric
                      BaTiO$_{3}$ (BTO) were produced and investigated for their
                      structural and magnetic properties. The combination of these
                      ferroic properties can lead to an artificial multiferroic. A
                      possible magnetoelectric coupling at the interface was
                      proposed by Burton et al. [1]. Thus, special emphasis was
                      given to the manipulation of magnetic properties by applying
                      electric fields. A magneto-electric coupling could be
                      observed in the heterostructures under investigation.
                      Epitaxial LSMO thin films were grown on BTO substrates using
                      a state-of-the-art oxide molecular beam epitaxy (OMBE) and a
                      high oxygen sputtering system (HOPSS). Stoichiometric
                      La$_{1-x}$Sr$_{x}$MnO$_{3}$ films with doping levels of x =
                      0.5 and x = 0.3 were produced. The film quality in terms of
                      roughness and crystalline structure was confirmed by X-ray
                      scattering methods. The presence of structural domains in
                      the BaTiO$_{3}$ single crystal substrate, whose proportion
                      could be altered due to the application of electric fields,
                      was shown by X-ray diffraction. Tensile strain is induced
                      into the epitaxial La$_{1-x}$Sr$_{x}$MnO$_{3}$ films in the
                      whole temperature range under investigation. The
                      magnetization of LSMO alteres by the variation of strain
                      induced into the film, generated by the different structural
                      phases of single crystal BaTiO$_{3}$ substrates. The
                      magnetization shows sharp steps at the structural phase
                      transition temperatures of BTO. The evaluation of magnetic
                      hysteresis loops reveals a change of the magnetic anisotropy
                      of LSMO for each structural phase of BTO, but also within
                      the orthorhombic phase. Special focus was given to the
                      manipulation of magnetic properties by the application of
                      electric fields. A newly established measurement option was
                      used to determine the magnetic response to an applied
                      electric field as a function of temperature and magnetic
                      field. The electrically induced modification of the
                      magnetization is profound near the structural phase
                      transition temperatures. Electrical hysteresis loops give a
                      detailed view on the influence of the electric field on the
                      magnetization. The magnetic coercivity field shifts by the
                      application of electric fields giving rise to a change of
                      the magnetic anisotropy. Polarized neutron reflectivity
                      measurements yield the magnetization profiles of the
                      LSMO/BTO heterostructures to clarify a limitation of the
                      effect to the interface. Samples grown by OMBE indicate a
                      better epitaxial crystal structure due to a strain induced
                      reduction in the magnetization at the interface. Samples
                      produced by HOPSS show a reduced magnetization for higher
                      layer thicknesses, which might be related to oxygen
                      vacancies. Simulations of the polarized neutron reflectivity
                      data for different electric field directions reveal that the
                      observed differences in the reflectivity are mostly related
                      to altered structural properties. Several mechanisms, which
                      might be responsible for the observed effects in LSMO on
                      BTO, are discussed. Strain effects via the elastic channel
                      can lead to a rotation of the magnetican isotropy, a change
                      of the orbital ordering or the exchange interaction. Also
                      carriermediated effects and oxygen diffusion under applied
                      electric fields have to be considered. Furthermore, the
                      ferroelectric properties of the BaTiO$_{3}$ substrates and
                      their response to the electric field is of crucial
                      importance to explain the observed effects.},
      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-MLZ)SNS-MR-20160304 / EXP:(DE-MLZ)MARIA-20140101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/283618},
}