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@ARTICLE{Engelmann:892540,
      author       = {Engelmann, Ulrich M. and Shalaby, Ahmed and Shasha, Carolyn
                      and Krishnan, Kannan M. and Krause, Hans-Joachim},
      title        = {{C}omparative {M}odeling of {F}requency {M}ixing
                      {M}easurements of {M}agnetic {N}anoparticles {U}sing
                      {M}icromagnetic {S}imulations and {L}angevin {T}heory},
      journal      = {Nanomaterials},
      volume       = {11},
      number       = {5},
      issn         = {2079-4991},
      address      = {Basel},
      publisher    = {MDPI},
      reportid     = {FZJ-2021-02141},
      pages        = {1257 -},
      year         = {2021},
      abstract     = {Dual frequency magnetic excitation of magnetic
                      nanoparticles (MNP) enables enhanced biosensing
                      applications. This was studied from an experimental and
                      theoretical perspective: nonlinear sum-frequency components
                      of MNP exposed to dual-frequency magnetic excitation were
                      measured as a function of static magnetic offset field. The
                      Langevin model in thermodynamic equilibrium was fitted to
                      the experimental data to derive parameters of the lognormal
                      core size distribution. These parameters were subsequently
                      used as inputs for micromagnetic Monte-Carlo
                      (MC)-simulations. From the hysteresis loops obtained from
                      MC-simulations, sum-frequency components were numerically
                      demodulated and compared with both experiment and Langevin
                      model predictions. From the latter, we derived that
                      approximately $90\%$ of the frequency mixing magnetic
                      response signal is generated by the largest $10\%$ of MNP.
                      We therefore suggest that small particles do not contribute
                      to the frequency mixing signal, which is supported by
                      MC-simulation results. Both theoretical approaches describe
                      the experimental signal shapes well, but with notable
                      differences between experiment and micromagnetic
                      simulations. These deviations could result from Brownian
                      relaxations which are, albeit experimentally inhibited,
                      included in MC-simulation, or (yet unconsidered)
                      cluster-effects of MNP, or inaccurately derived input for
                      MC-simulations, because the largest particles dominate the
                      experimental signal but concurrently do not fulfill the
                      precondition of thermodynamic equilibrium required by
                      Langevin theory.},
      cin          = {IBI-3},
      ddc          = {540},
      cid          = {I:(DE-Juel1)IBI-3-20200312},
      pnm          = {524 - Molecular and Cellular Information Processing
                      (POF4-524)},
      pid          = {G:(DE-HGF)POF4-524},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {34064640},
      UT           = {WOS:000657045100001},
      doi          = {10.3390/nano11051257},
      url          = {https://juser.fz-juelich.de/record/892540},
}