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@BOOK{Thakuria:838471,
      author       = {Thakuria, Pankaj},
      title        = {{M}agnetic structure in relation to the magnetic field
                      induced ferroelectricity in {Y}-type hexaferrite
                      {B}a$_{2−x}${S}r$_{x}${Z}n$_{2}${F}e$_{12}${O}$_{22}$},
      volume       = {151},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2017-07074},
      isbn         = {978-3-95806-250-4},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {180 S.},
      year         = {2017},
      note         = {RWTH Aachen, Diss., 2017},
      abstract     = {This thesis consists of in depth study of spin structure of
                      magnetoelectric Y-type hexaferrite
                      Ba$_{2−x}$Sr$_{x}$Zn$_{2}$Fe$_{12}$O$_{22}$ system.
                      Magnetoelectric and multiferroic materials are of high
                      interest from information technology point of view, but
                      traditional mechanism of magnetism and ferroelectricity
                      makes it rare to observe both in single phase materials. One
                      of the most widely studied non conventional mechanism where
                      cross coupling of magnetism and ferroelectricity takes place
                      in non-collinear spin systems is spin driven
                      ferroelectricity by inverse Dzyaloshinskii-Moriya (IDM)
                      mechanism or spin currect mechanism (SC). The spin
                      frustration leading to non-collinear spin arrangements also
                      leads to low magnetic ordering temperature hinders room
                      temperature realization of magnetoelectric coupling effect.
                      Hexaferrite systems are an answer to high temperature
                      magnetoelectric behavior in single phase materials. Y-type
                      hexaferrite with composition
                      Ba$_{2−x}$Sr$_{x}$Zn$_{2}$Fe$_{12}$O$_{22}$ was the first
                      hexaferrite to show magnetoelectric behavior, where a 2-fan
                      planar spin structure was proposed, not compatible with the
                      magnetic field (H) induced ferroelectricity by IDM/SC
                      mechanism. In depth investigation of the spin structure and
                      its relationship with macroscopic field driven
                      ferroelectricity was the central point of this thesis. The
                      widely accepted spin structure of Y-type hexaferrite is a
                      spin block model with large (L) and small (S) spin blocks,
                      collinear in spin arrangements inside the blocks but between
                      the blocks arrangements changes from collinear to spiral
                      depending upon the chemical composition. With change in the
                      Sr content in the composition
                      Ba$_{2−x}$Sr$_{x}$Zn$_{2}$Fe$_{12}$O$_{22}$ spin structure
                      was reported to change from collinear to in plane spiral in
                      earlier studies. The change in spin structures were easily
                      visible in magnetization curves, when magnetic field was
                      applied perpendicular to c-axis. In three samples with
                      x=1.4,1.18 and 0.72 grown by flux methods, our refinement of
                      single crystal x-ray diffraction data shows that Sr
                      substitution causes local distortion and change in
                      occupancies of Zn in the tetrahedral site which happens to
                      be in the spin block boundary, accompanying a change in the
                      Zn/Fe-O bond length. We speculate that the cumulative effect
                      of local distortion, change in occupations of Zn and bond
                      length change changes the superexchange interaction near the
                      block boundary changing the spinstructure. [...]},
      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)BIODIFF-20140101 / EXP:(DE-MLZ)DNS-20140101},
      typ          = {PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/838471},
}