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SYA: Symposium Kolloide Systeme und Polyelektrolyte
SYA 4: Kolloidale Systeme und Polyelektrolyte
SYA 4.4: Poster
Montag, 9. März 1998, 18:00–20:00, P1
Order and dynamics of paramagnetic colloids in 2D — •K. Zahn1, J. Mendez-Alcaraz2, and G. Maret1 — 1Fakult"at f"ur Physik,Universit"at Konstanz, Universit"atsstr. 10,78434 Konstanz — 2Institut Charles Sadron,6 rue Boussingault, 67083 Strasbourg CEDEX,France
We discribe a novel colloidal model system suited to study structural and dynamic features of two-dimensional (2D) fluids and crystals. A 2D-layer of iron-oxide doped latex particles at a water/air interface is prepared. A magnetic field is applied perpendicular to the layer generating a repulsive dipole-dipole interaction between the particles. Below (above) a concentration dependent critical field a 2D liquid (or crystal, respectively) is formed.
Using video-microscopy we have studied pair correlation functions g(r) and time dependent selfdiffusion constants D(t). In contrast to hard sphere systems we observed an enhancement of D(t) due to hydrodynamic interaction [1]. Furthermore crystallization and melting points are determined using the translational and orientational correlation functions, the 2D Lindemann criterion and the number of defects in the system. We find - surprisingly - evidence for a two stage melting scenario associated with hysteresis.
[1] K. Zahn, J. Medez-Alcaraz, G. Maret, Phys. Rev. Lett. 79(1), 175 (1997)