Resonance Circuit with a Nonlinear Liquid Crystal Capacitor

The liquid crystal 4'octyl-4-cyanobiphenyl (8CB) was injected into a commercially available liquid crystal capacitor cell (INSTEC, Inc). The cell was housed in a temperature-controlled environment constructed in the lab and a resonant circuit was assembled using the 8CB capacitor. The temperature of the capacitor was varied over the range 25\r{ }C to 45\r{ }C, covering the smectic, nematic, and isotropic phases. The sample was held at each temperature with a precision of 1mK before measuring the resonance curve with a network analyzer. The results showed a non-linearity in the resonance curve in the nematic phase, distorting the shape of the resonance curve. The corresponding curves for the smectic and isotropic phases were linear.