Magnetically Induced Structural Difference in Ferrofluids and Magnetorheological Fluids

We have prepared ferrofluid using magnetic nanoparticles (similar to 10 nm) and magnetorheological fluid (MR fluid) using micron size (similar to 10 mu m) magnetic particles. We have observed striking difference in magnetically induced structure formation in both the fluids although both are classifications of magnetic fluids in a broad way. A field induced structural difference in chain formation, labyrinthine pattern, spikes formation (Rosensweig surface instability) and optical diffraction pattern is observed. The induced structural difference is mainly due to the magnetically induced dipolar interaction, field induced viscosity and surface tension in both the fluids.