Chaotic routes to colloidal molecules

We present computer simulation and experiments on dilute suspensions of superparamagnetic particles subject to rotating magnetic fields. ~We focus on short chains of particles and their decay routes to stable structures. ~At sufficiently high rates, the typical behavior of a small set of particles, initially aligned in a chain along the axis of the field is to go through a period of chaotic motion and, after some time to decay into one of a number of possible periodic orbits with a compact spatial structure. Transition between these periodic orbits is also possible and will depend on both rotation rate and finite temperature.~We show the entry into and transitions between periodic orbits is an activated process with no memory and report on associated rate constants for the transitions.