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@PHDTHESIS{Wang:847883,
      author       = {Wang, Liming},
      title        = {{M}anipulation of magnetism in iron oxide nanoparticle /
                      {B}a{T}i{O}$_{3}$ composites and low-dimensional iron oxide
                      nanoparticle arrays},
      volume       = {180},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2018-03209},
      isbn         = {978-3-95806-351-8},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {VI, 151 S.},
      year         = {2018},
      note         = {RWTH Aachen, Diss., 2018},
      abstract     = {Ferrimagnetic (FiM) iron oxide nanoparticles (NPs) on top
                      of ferroelectric BaTiO$_{3}$(BTO) substrates were prepared
                      and a magnetoelectric coupling (MEC) effect was observed in
                      the heterostructures. Iron oxide NPs first were
                      self-assembled as amonolayer on top of BTO substrates.
                      Grazing incidence small angle x-ray scattering(GISAXS) and
                      scanning electron microscopy (SEM) confirm a close-packed
                      hexagonal order of the NP monolayers. By inserting a Ti
                      layer and further capping with an Au layer, an enhanced MEC
                      effect was observed. Scanning transmission electron
                      microscopy (STEM) provides information about the layer
                      structure of the sample. The magnetization shows sharp
                      magnetization jumps at the phase transition temperatures of
                      the BTO substrate. Electric field manipulation of magnetism
                      was performed using a superconducting quantum interference
                      device (SQUID) setup with an electric field implemented. A
                      butterfly shaped curve of the magnetic moment vs. DC
                      electric field was obtained which is coincident with the
                      piezoelectric response of BTO single crystals which confirms
                      a strain mediated MEC. The magnetoelectric ac susceptibility
                      (MEACS) signal as function of temperature under an AC
                      electric field shows abrupt jumps at the BTO phase
                      transition temperatures. The magnetic depth profiles of NP
                      monolayers at various applied DC electric fields were
                      deduced from polarized neutron reflectivity (PNR) results.
                      Fitting of the data shows that the observed differences in
                      reflectivity curves are caused by the changed structural
                      properties of the substrate and layers as a major factor and
                      the altered magnetism of NP monolayers as a minor factor.
                      Also iron oxide NPs self-assembled on BTO films on Nb doped
                      SrTiO$_{3}$ (Nb doped STO) substrates were prepared. The DC
                      electric field vs. magnetization and MEACS results indicate
                      that there is a MEC between NPs and the BTO film. Interface
                      charge and strain transfer are responsible for the MEC
                      effects. Moreover, NPs self assembled into trench-patterned
                      silicon (Si) substrates were prepared to investigate the
                      magnetic anisotropy and collective magnetic behavior. The
                      magnetization vs. magnetic field shows a large shape-induced
                      magnetic anisotropy effect. After the application of a
                      magnetic saturation field along the trenches, electron
                      holography results show that an overall magnetic ordered
                      state exists in the nanoparticle assemblies. In the
                      direction of the trenches, the NPs exhibit a ferromagnetic
                      (FM) -like ordered state and a small memory effect was
                      observed. Whereas large memory effect was observed
                      perpendicular to the trenches. We conclude that the FM
                      ordered state suppresses a superspin glass state of the
                      dipolarly coupled NP moments. This work opens up viable
                      possibilities for energy-efficient electronic devices
                      fabricated by simple self-assembly techniques.},
      cin          = {JCNS-2 / PGI-4 / JARA-FIT / JCNS-FRM-II},
      cid          = {I:(DE-Juel1)JCNS-2-20110106 / I:(DE-Juel1)PGI-4-20110106 /
                      $I:(DE-82)080009_20140620$ /
                      I:(DE-Juel1)JCNS-FRM-II-20110218},
      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)MARIA-20140101 / EXP:(DE-MLZ)SPODI-20140101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/847883},
}