Substrate-induced phase transitions in two-dimensional colloidal systems

We study the phase behavior of a 2D colloidal system in the presence of an external periodic 1D potential. As colloidal suspension we use an aqueous suspension of superparamagnetic spheres with a diameter of 4.5 μm. The periodic 1D potential is fabricated by evaporation of thin magnetic nickel lines onto a glass substrate, which is afterwards covered with a protective poly(methyl methacrylate) layer. When the phase behavior of the colloidal system is investigated as a function of the applied external magnetic field, we observe a promoting effect of the underlying periodic 1D potential to the crystallization of the 2D colloidal system.