Ferrofluids are colloidal suspensions of 100 Angstrom scale magnetic grains. As a superparamagnet, this fluid has extraordinary response to applied fields, leading to many useful commercial applications. The disordered fluid state may contain long chains of grains connected by their magnetic attraction. At high magnetic strength and volume fraction the fluid may phase separate or even become spontaneously aligned. Using mean field theory and Monte Carlo simulation Widom investigates magnetic susceptibility and phase transitions of this complex fluid.
Recent studies examine polarization textures and droplet shapes of spontaneously magnetized liquids.
Other research interests include hydrodynamic pattern formation , gel electrophoresis and reptation of DNA , and the structure of metallic glass. Extension to ternary phase diagrams Phys. S. Banerjee and M. Widom, Ferromagnetic liquid thin films under applied field Phys. J.A. Miranda and M. Widom, Parallel flow in Hele-Shaw cells with ferrofluids Phys. A.I. Goldman, et al.