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@INPROCEEDINGS{Nandakumaran:866615,
      author       = {Nandakumaran, Nileena and Köhler, Tobias and Barnsley,
                      Lester and Feygenson, Mikhail and Feoktystov, Artem and
                      Petracic, Oleg and Brückel, Thomas},
      title        = {{M}agnetic small-angle neutron scattering from
                      self-assembled iron oxide nanoparticles influenced by field},
      reportid     = {FZJ-2019-05696},
      year         = {2019},
      abstract     = {Self-assembly of magnetic nanoparticles, in general, is of
                      interest due to the broad range of applications in material
                      science and biomedical engineering [1,2]. Parameters that
                      affect self-assembly in nanoparticles include particle size,
                      the applied magnetic field profile, concentration and
                      synthesis routines [3]. A range of different sizes of iron
                      oxide nanoparticles between 17 and 27 nm were investigated
                      using polarized small-angle neutron scattering (SANS) at the
                      KWS-1 instrument operated by the Jülich Centre for Neutron
                      Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ) in
                      Garching, Germany. Nanoparticles were dispersed in toluene
                      and measured at room temperature in a range of applied
                      fields between ±2.2 T. The observed self-assembly strongly
                      depended on both nanoparticle size and applied field. For
                      smaller particles (diameter ≤ 20 nm), there was no
                      indication of self-assembly even at high concentration
                      $(1\%$ v/v), while 27 nm nanoparticles assemble into linear
                      chains even in low concentrations $(0.42\%$ v/v) and low
                      field.The smallest nanoparticles (d = 17 nm) were studied by
                      contrast variation; by altering the isotopic composition of
                      the toluene solvent, the magnetization profile within the
                      cores of the nanoparticles could be extracted with
                      high-resolution when using a spin-polarized incident neutron
                      beam [4]. For larger nanoparticle, the structural and form
                      factors were obtained by sector analysis of the 2-D SANS
                      patterns (Fig. 1(a) and (b)). The extracted structure
                      factors suggest that the chains grow longer and straighter
                      and align more closely with the field direction up until
                      application of the maximum field (Fig. 1(c)). This is
                      understood in terms of a minimization of the dipole energy
                      of the nanoparticles in the presence of the applied field
                      and neighbouring particles. The implications for the control
                      of self-assembly of more complex nanoparticles will be
                      discussed.[1] G. Ozina, K. Hou, B. Lotsch, L. Cademartiri,
                      D.Puzzo, F. Scotognella, A. Ghadimi, J. Thomson, Materials
                      Today, Vol. 12, p.12 (2009)[2] P. Tartaj, Current
                      Nanoscience, Vol. 2, p.43 (2006) [3] Z. Fu, Y. Xiao, A.
                      Feoktystov, V. Pipich, M. Appavou, Y. Su, E. Feng, W. Jin
                      and T. Brückel, Nanoscale, Vol. 8, p.18541 (2016)[4] A.
                      Wiedenmann, Journal of Applied Crystallography, Vol. 33,
                      p.428 (2000)},
      month         = {Nov},
      date          = {2019-11-04},
      organization  = {64th Annual Conference on Magnetism
                       and Magnetic Materials, Las Vegas
                       (United States), 4 Nov 2019 - 8 Nov
                       2019},
      subtyp        = {After Call},
      cin          = {JCNS-FRM-II / JCNS-1 / JCNS-2 / MLZ},
      cid          = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-1-20110106 / I:(DE-Juel1)JCNS-2-20110106 /
                      I:(DE-588b)4597118-3},
      pnm          = {524 - Controlling Collective States (POF3-524) / 6212 -
                      Quantum Condensed Matter: Magnetism, Superconductivity
                      (POF3-621) / 6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich
                      Centre for Neutron Research (JCNS) (POF3-623)},
      pid          = {G:(DE-HGF)POF3-524 / G:(DE-HGF)POF3-6212 /
                      G:(DE-HGF)POF3-6G15 / G:(DE-HGF)POF3-6G4},
      experiment   = {EXP:(DE-MLZ)KWS1-20140101},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/866615},
}