Non-linear alignment dynamics in suspensions of platelets under rotating magnetic fields

Under rotating magnetic fields, micron-sized platelets suspended in a fluid and decorated with magnetic nanoparticles are found to assume two orientational states. This behavior is very attractive for the development of unusual reinforcement architectures in synthetic composites. However, it is highly dependent on the frequency of the magnetic field and the rheological properties of the fluid. At low frequencies or fluid viscosities, the magnetized platelets continuously rotate in the fluid. At high frequencies and fluid viscosities, a non-linear response is observed in which the platelets align parallel to the plane of the rotating field. In this study we offer a theoretical description and experimental verification of this phenomenon, which can be used to build composites with fully aligned platelet reinforcement.