  Based on Dynamical Density Functional Theory (DDFT) we investigate a binary
mixture of interacting Brownian particles driven over a substrate via a
one-dimensional ratchet potential. The particles are modeled as soft spheres
where one component carries a classical Heisenberg spin. In the absence of a
substrate field, the system undergoes a first-order fluid-fluid demixing
transition driven by the spin-spin interaction. We demonstrate that the
interplay between the intrinsic spinodal decomposition and time-dependent
external forces leads to a novel dynamical instability where stripes against
the symmetry of the external potential form. This structural transition is
observed for a broad range of parameters related to the ratchet potential.
Moreover, we find intriguing effects for the particle transport.
