This condensed matter physics research project will investigate magnetic-field-induced instabilities in magnetic fluids, sometimes known as ferrofluids. The magnetic fluids contains suspensions of magnetic nanoparticles. When exposed to a magnetic field, the fluid surface, as well as volume elements, undergo topological distortions. The mechanism for the distortion is a non-uniform magnetic body force, arising from spatial inhomogenieties in the magnetic susceptibility of the fluids through either temperature or particle concentration gradients. A series of experimental and theoretical analyses will study the fluid behavior. Experiments will focus on (a) conditions responsible for the onset of the instabilities, (b) effects of external parameters on the patterns displayed by the fluids, (c) effects of boundary conditions, and (d) the role of thermal diffusion or the Soret effect on the instabilities. Linear and non-linear theories for the systems will be developed. The results of the research will have broad application in chemical reactions, biological pattern-formation, field-controlled heat-transfer devices, and crystal growth controlled by external forces. The project provides excellent training for graduate students in a highly inter-disciplinary research field. %%% This condensed matter physics research project investigates magnetic-field-induced instabilities in magnetic fluids, sometimes known as ferrofluids. A magnetic fluid consists of magnetic nanoparticles suspended in nonmagnetic solvent. Because each particle possesses a net moment, the fluid will respond to applied magnetic fields. Earlier research has shown that instabilities occur when the applied field exceeds a critical value. In this proposal, both experimental and theoretical work will be performed to explore the mechanisms responsible for these instabilities. Experiments will be focused on (a) conditions for the onset of instabilities; (b)effects of external parameters on pattern selection; (c) effects of boundary conditions; and (d) the role of thermal diffusion on these instabilities. Linear and nonlinear theories for this system are proposed. Results from this proposed work will have not only the fundamental significance in understanding the effects of symmetry breaking in physical systems in general, but also broad applications in chemical reactions, biological pattern-formation, field-controlled heat-transfer devices, and crystal growth controlled by external forces. The work on surface tension will result in applications in surface science. Further study on controlling instabilities involving gravity will be very useful in developing magnetic levitation in magnetic fluid environments. The project provides excellent training for graduate students in a highly inter-disciplinary research field. ***
