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 proposed as a means to investigate the real and imaginary components of the dielectric permittivity of liquid crystals in external electric and magnetic fields. Results are given for measurements of a 500 MHz oscillator frequency for two types of nematic crystals, 5CBP and MBBA. Fundamental regularities are identified in the behavior of the microwave 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 the molecules are oriented parallel to the direction of the microwave electric field. Zh. Tekh. Fiz. 68, 117–121 (January 1998)