LABYRINTHINE PATTERN-FORMATION IN MAGNETIC FLUIDS

A quasi two-dimensional drop of a magnetic fluid (ferrofluid) in a mag netic field is one example of the many systems, including amphiphilic monolayers, thin magnetic films, and type I superconductors, that form labyrinthine patterns. The formation of the ferrofluid labyrinth was examined both experimentally and theoretically. Labyrinth formation wa s found to be sensitively dependent on initial conditions, indicative of a space of configurations having a vast number of local energy mini ma. Certain geometric characteristics of the labyrinths suggest that t hese multiple minima have nearly equivalent energies. Kinetic effects on pattern selection were found in studies of fingering in the presenc e of time-dependent magnetic fields. The dynamics of this pattern form ation was studied within a simple model that yields shape evolutions i n qualitative agreement with experiment.