Dielectric anomalies and phase transition in glycinium phosphite crystal under the influence of a transverse electric field

The dielectric properties of glycinium phosphite (GPI) crystals as a function of temperature and electric field magnitude are investigated. The electric field E is applied perpendicularly to the ferroelectric b-axis in the direction of hydrogen-bonded phosphite chains in the crystal (the c-axis). The shift of the paraelectric-ferroelectric phase transition to lower temperatures proportionally to Ec2 (where Ec is an effective field in the sample) is observed. Strong anomalies in the field dependence of the permittivity ε'c in the temperature region T ≤ Tc are revealed. It is shown that the observed jump-like changes of ε'c are caused by the phase transition from the ferro- to paraelectric phase induced by the electric field. Such a transition is connected with the rearrangement of protons on hydrogen bonds and the reversal of the corresponding dipole moments, at which the compensation of their components along the b-axis takes place. The theoretical description of the observed dielectric anomalies, given on the basis of the phenomenological Landau free energy approach, is in good agreement with the experimental data