Theoretical and experimental studies about the influence of an external magnetic field on a nematic liquid crystal with carbon nanotubes adding are presented. Planar oriented cells filled with a mixture of MCL-6601 (Merck) nematic and multi-walled carbon nanotubes were subjected to a magnetic field higher than the critical one for the magnetic Freedericksz transition. A laser beam was used to observe the molecular director distortion. Dynamical measurements of the transmitted light intensity were performed when the magnetic field was switched on and off. The results were used to evaluate the relaxation times of the mixture and to show the influence of the carbon nanotubes on these parameters. We also present a theoretical model to explain the experimental results.
Nonlinear phenomena induced by an electric field inside a nematic liquid crystal were studied. A planar oriented cell filled with 5CB nematic liquid crystal was subjected to an external voltage, higher than the threshold value for the Freedericksz transition, and a laser beam was sent perpendicular to the cell. Circular fringes appeared on the screen. The maximum number of diffraction fringes for different voltage values was measured and the experimental plot were in good agreement with theory. We performed a set of dynamic measurements of the fringes evolution from the moment when the laser beam was applied until the maximum number of fringes was reached, for each voltage, and the results were consistent with theoretical pattern.