Berlin 2015 – scientific programme

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MA: Fachverband Magnetismus

MA 38: Magnetic Nanoparticles

MA 38.9: Talk

Thursday, March 19, 2015, 11:45–12:00, H 0110

Phase formation in colloidal systems with tunable interaction — •Hauke Carstensen, Vassilios Kapaklis, and Max Wolff — Dept of Physics & Astronomy, Box 516, SE-751 20 Uppsala, Sweden

Self assembly is one of the most fascinating phenomena in nature and one key component in the formation of hierarchic structures forming the basis for living organisms. The formation of structure depends critically on the interaction between the different constituents. We have realized a two dimensional system of colloidal particles with tunable magnetic dipole forces. Particles with a diameter in the micrometer range are embedded in a magnetic medium, which is composed of nanometer sized magnetic particles dispersed in water. The result is an effective magnetic susceptibility of the embedded particles which can be altered by the concentration of nanoparticles. The phase formation and diagram of the micrometer particles are studied by transmission optical microscopy. For in-plane magnetic fields we report a phase transition from hexagonal to cubic, when tuning the magnetic interaction between the individual particles from antiferromagnetic to ferrimagnetic. Quantitatively information is extracted from the pair correlation function and explained by the dipolar particle interaction. For out-of plane fields the phase diagram is more rich and is mapped for different particle ratios and concentrations.