Structure and dynamics of repulsive magnetorheological colloids in two-dimensional channels

We study a system of colloidal spheres with induced magnetic dipoles confined in two-dimensional (2D) hard-wall channels using Brownian dynamics simulations. The external magnetic field is directed normal to the 2D plane and therefore the colloids interact with a purely repulsive r(-3) potential. The effects of confinement between parallel walls are determined by analyzing the structure and dynamics of these confined systems and comparing to the unbounded (infinite) 2D plane limit. The bond-order correlation function is analyzed as a function of time and exhibits unique characteristics associated with the channel-like confinement. The existence of a plateau in this correlation function is observed over an intermediate time scale and the fate of the plateau (decay or persistence) depends upon the channel width, the strength of the external magnetic field, and the number density. The plateau is analyzed in further detail and an explanation is put forth for its existence and subsequent long time behavior. Additionally, re-entrant behavior with respect to dimensionless channel width is observed in the structural properties and an associated state-diagram is presented for these systems.