Measurement of spontaneous polarisation by field reversal

Abstract

The measurement of spontaneous polarisation in ferroelectric smectic-C liquid crystals is discussed. The method employed is that of field reversal and a new approach is described for the background current to be subtracted electronically from the current during switching to derive the component due to the polarisation realignment. This is achieved by means of a compensating circuit formed of discrete components. The operating principle, circuitry, setting up and calibration procedures are described in detail. Possible drive waveforms are compared and sample results are presented.