A detailed study of a novel material exhibiting antiferro-, ferri-, and ferroelectric phases has been undertaken. The tilt angle, spontaneous polarisation and the dynamics of the helical unwinding have been examined as a function of temperature and voltage in all the phases of interest. The material exhibits large tilt angles (-31°) and values of spontaneous polarisation (~100nCcM-2) in cases where the helix is totally unwound. The behaviour of tilt angle as a function of applied electric field is examined in the ferri- and antiferro-electric phases. A stepwise increase in tilt angle as a function of applied voltage in the ferri-electric phase is presented, as well as unusual behaviour in the antiferro-electric state. In addition, a preliminary investigation of the change in spontaneous polarisation as a function of pressure is presented. It is shown that the dependence of spontaneous polarisation in the ferroelectric phase is relatively weak.
ASJC Scopus subject areas
- Condensed Matter Physics