One of the most exciting areas in colloid research is the control of interparticle
interactions to generate new structures. The ease of tuning interactions, size, shape,
and composition has made these nano- and micrometer sized particles appealing
probes for a number of fundamental studies. I will describe how time-varying
magnetic fields drive a suspension of superparamagnetic colloids to undergo phase
transitions that display interesting collective fluctuations. Particle tracking allows us
to see these “colloidal atoms” to track the nucleation of crystals or the dynamics of
spinodal decomposition from a metastable liquid. I will attempt to answer the
question: can classical thermodynamic expressions be applied to these field-driven
colloidal systems?