The effects of magnetic nanoparticles on oscillating behavior of a nematic liquid crystal cell

ABSTRACT

Magnetic suspensions in anisotropic host fluids such as liquid crystals show interesting behavior that have attracted vast interest in many areas of science, technology, and medicine. Recently, suspensions of monodomain magnetic nanoparticles in nematic liquid crystals, called ferronematics, are extensively used in different technological applications. Dynamical ordering behavior in these magnetic materials is a complex subject due to several dynamic cross-couplings. In this work, the effects of magnetic nanoparticle dopants on the dynamical behavior of a nematic liquid crystal cell are discovered through studying the motion of a torsional oscillator in which the cell is contained. Dynamical features of the cell are investigated within the framework of continuum theory. The hydrodynamic equations of the ferronematic liquid crystal are calculated in the presence of an applied magnetic field. The velocity components and the displacement dependence of the velocity field in the cell are obtained. Then, the toque exerted on the cell contained in torsional oscillator is determined. This study is based on Leslie–Ericksen theory. The analysis is also used to study the resonant frequency as a function of the applied field. In this way, the key roles of the entropy of ferroparticle solution and anchoring induced ferronematic interactions become evident.

KEYWORDS:

• Fredericks transition
• liquid crystal
• nanoparticles
• stress tensor

Acknowledgments

We would like to thank Prof. Shahzamanian and Ms. F. Rabyee for previous collaborations that have motivated this work and also for helpful discussions.