Anomalous Non-linear Dielectric Behaviour of LATGS Crystals

The dielectric permittivity in a biasing electric field and also the spontaneous polarization of LATGS crystals are measured near the ferroelectric phase transition. It is demonstrated that L-alanine admixtures change the parameters of dielectric state equation. It is shown that the bias field value decreases while approaching the phase transition temperature from the para-electric phase. The effective non-linearity coefficient B, near Tc, depends on electric field direction. This anomalous non-linear behaviour can be explained assuming asymmetric bias field dependence on external electric field.