Two-dimensional colloidal systems in time-dependent magnetic fields

摘要: We use super-paramagnetic colloidal particles confined by gravitation to a flat water-air interface as model system study the non-equilibrium liquid-solid phase transition in two dimensions. The temperature is adjustable changing strength of an external magnetic field perpendicular interface. Increasing on timescale milliseconds quenches liquid strongly super-cooled state. If cooled down out equilibrium solidification differs drastically from melting and freezing scenario no hexatic observable. solidifies polycrystalline structure with many grains different orientations. Since local closed packed order dimensions sixfold, both fluid crystalline state, sensitive measures have be developed. In present manuscript we compare methods identify cluster locally motivate threshold values. Those are chosen comparison isotropic one hand large mono-crystals thermal other hand. With given criteria for found not circular fractal given.