Influence of Electric and Magnetic Fields on the Microwave Dielectric Constant of a Liquid Crystal with a Positive Dielectric Anisotropy

Abstract

The dielectric constant and loss in the anisotropic and normal liquid phases of anisal-p-aminoazobenzene were measured at frequencies of 6 and 24 kMc/sec. Measurements were made with an external magnetic field parallel and perpendicular to the microwave electric field at both frequencies while the measurements in the presence of an external electric field were made at only 6 kMc/sec with the external electric field parallel to the microwave electric field. Results in the presence of an external magnetic field were similar to those for p-azoxyanisole and anisaldazine which have a negative dielectric anisotropy. Measurements in the presence of an external electric field indicate that the alignment of the molecules due to low frequency ac fields is comparable to that produced by magnetic fields providing saturation is reached. Disturbances which were due to an electric field appeared to have an appreciable effect on the alighment when dc fields were applied, but this was not observed for ac fields with frequencies between 20 and 300 000 cps.