8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.128Wed 711:10-14:00The structure factor of magnetic colloidsElena Pyanzina, 1 Joan Cerda, 2 Christian Holm, 3 and Sofia Kantorovich 31 Ural State University, Lenin av. 51, 620000, Ekaterinburg, Russian Federation2 Institute for Cross-Disciplinary Physics and Complex System, Palma de Mallorca,Spain3 Institute for Computational Physics, University of Stuttgart, Stuttgart, GermanyWe investigate magnetic colloids, which consist of single-domain magnetic particles in a magnetopassiveliquid environment. Recent investigations have shown that the microstructure of magneticcolloids appears to be much more complicated than the previously expected structure of aliquid state. Strong response to an external magnetic field, represented by ferrocolloids in combinationwith a liquid state, give rise to numerous applications of magnetic colloids in engineeringand arts. For these systems the chains of the magnetic particles are the most probable microstructureunits. One of the possible experimental techniques to investigate the microstructure of ferrocolloidsis the small angle neutron scattering (SANS). With SANS one measures the structurefactor. We have developed a theoretical model for calculating the structure factor for ferrocolloidswith chain aggregates for both mono- and bidisperse systems in the absence of an applied magneticfield, and we have proposed a simple way to handle the influence of magnetic field. Our method isbased on the explicit construction of radial distribution functions from chain distributions obtainedfrom the density functional minimization. An extensive comparison of the theoretical model to theresults of molecular dynamics simulation showed a very good agreement for mono- and bidispersesystems. We hope that the developed method can be used to analyze scattering images obtainedexperimentally for real magnetic colloids, for example for cobalt ferrocolloids. Moreover, our developedcombined approach can help to reveal a direct connection between experimental data forthe SANS and microstructural observables, which is hardly possible using theory, experiments orsimulations separately.128