Phase transitions in magnetic rods driven by dynamic magnetic fields

Magnetic fields can remotely, and precisely, drive magnetic matter into far-from-equilibrium states. We use molecular dynamics to study phase transitions in stiff filaments composed of superparamagnetic colloids in precessing magnetic fields. By controlling the magnetic torque that drives filament precession, we observe transitions from paranematic to smectic states. Furthermore, the inter-filament magnetic coupling directly affects the local alignment of the filaments, producing disordered to hexagonal order transitions. These results show how time-dependent magnetic fields can navigate the phase space of dense solutions of magnetic colloidal structures.