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@INPROCEEDINGS{Steffen:190001,
      author       = {Steffen, Alexandra and Pütter, Sabine and Mattauch, Stefan
                      and Schubert, Jürgen and Zander, Willi and Geprägs,
                      Stephan and Brückel, Thomas},
      title        = {{R}elation between deposition methods on magnetic depth
                      profile of [{L}a2/3{S}r1/3]x{M}ny{O}z/{S}r{T}i{O}3},
      reportid     = {FZJ-2015-02964},
      year         = {2014},
      abstract     = {In transition metal oxide thin films the exact control of
                      stoichiometry can explain phenomena like ferromagnetism or
                      superconductivity at interfaces of non-magnetic materials as
                      found in LaAlO3/SrTiO3[1]. Here, we show the influence of
                      growth modes on the magnetic depth profile of different
                      [La2/3Sr1/3] to Mn ratios in thin [La2/3Sr1/3]x[Mn]y[O]z
                      layers on SrTiO3 substrates via Polarized Neutron
                      Reflectometry.Via oxide Molecular Beam Epitaxy, it is
                      feasible to control not only the total stoichiometry of a
                      sample but additionally master an individual stoichiometry
                      for each atomic layer by individual operation of effusion
                      cell shutters for different elements. While co-deposition of
                      (La/Sr) and Mn lead to A site substitution of Mn in case of
                      Mn excess [2] in the perovskite structure ABO3, with
                      shuttered deposition it is feasible to grow different
                      crystal structures like members of the Ruddlesden−Popper
                      series [3]. We investigate this influence of nominally
                      identical stoichiometries onto the magnetic depth profile
                      via neutron reflectometry at TREFF@MLZ.Via two complementary
                      methods the films with typically 20 nm thickness were
                      prepared, on the one hand using conventional co-deposition
                      (La, Sr, and Mn shutters opened and closed simultaneously),
                      on the other hand via shuttered deposition (either La and Sr
                      shutters open or Mn shutter open). The Reflection High
                      Energy Electron Diffraction (RHEED) oscillations were
                      monitored to optimize the opening periods of Mn shutter or
                      (La/Sr) shutters.The stoichiometry of reference samples
                      [La2/3Sr1/3]1[Mn]1[O]3 was verified via Rutherford
                      Backscattering Spectroscopy (RBS). The growth rates for Mn,
                      La and Sr were calibrated by quartz crystal balance. X-ray
                      reflectivity measurements revealed for all films a roughness
                      well below 1nm which indicates a smooth surface, via X-ray
                      diffraction the out-of-plane lattice parameter was
                      determined and therefore the oxygen saturation was verified
                      [4]. The magnetic properties as function of varying the
                      (La/Sr):Mn ratio were determined via SQUID. The
                      ferromagnetic transition temperature shows a well-defined
                      dependency as function of Mn content; with increasing Mn
                      content the Curie temperature increases.References[1] M.
                      Warusawithana et al., Nat. Commun. 4, 2351 (2013)[2] C.
                      Aruta et al., Phys. Rev. B 86, 115132 (2012)[3] R. Palgrave
                      et al., J. Am. Chem. Soc. 134, 7700 (2012)[4] P. Orgiani et
                      al., Appl. Phys. Lett. 100, 042404 (2012)},
      month         = {Jul},
      date          = {2014-07-07},
      organization  = {13th surface x-ray and Neutron
                       scattering conference, Hamburg
                       (Germany), 7 Jul 2014 - 11 Jul 2014},
      subtyp        = {After Call},
      cin          = {JCNS (München) ; Jülich Centre for Neutron Science JCNS
                      (München) ; JCNS-FRM-II / JCNS-2 / PGI-9},
      cid          = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-2-20110106 / I:(DE-Juel1)PGI-9-20110106},
      pnm          = {422 - Spin-based and quantum information (POF2-422) / 424 -
                      Exploratory materials and phenomena (POF2-424) / 542 -
                      Neutrons (POF2-542) / 544 - In-house Research with PNI
                      (POF2-544) / 54G - JCNS (POF2-54G24)},
      pid          = {G:(DE-HGF)POF2-422 / G:(DE-HGF)POF2-424 /
                      G:(DE-HGF)POF2-542 / G:(DE-HGF)POF2-544 /
                      G:(DE-HGF)POF2-54G24},
      experiment   = {EXP:(DE-MLZ)TREFF-20140101},
      typ          = {PUB:(DE-HGF)24},
      url          = {https://juser.fz-juelich.de/record/190001},
}