A STUDY OF THE MICROWAVE DIELECTRIC PERMITTIVITY OF LIQUID-CRYSTALS IN ELECTRIC AND MAGNETIC-FIELDS

A microwave detector based on a self-sustained oscillator circuit is p roposed as a means to investigate the real and imaginary components of the dielectric permittivity of liquid crystals in external electric a nd magnetic fields. Results are given for measurements of a 500 MHz os cillator frequency for two types of nematic crystals, 5CBP and MBBA. F undamental regularities are identified in the behavior of the microwav e dielectric permittivity of samples in electric and magnetic fields. It is shown that the minimum of the high-frequency dielectric loss in liquid crystals correspond to a situation in which the long axes of th e molecules are oriented parallel to the direction of the microwave el ectric field. (C) 1998 American Institute of Physics. [S1063-7842(98)0 2201-6].