DIELECTRIC STUDY OF THE FERROELECTRIC PHASE-TRANSITION IN DMAGAS CRYSTAL

Electric permittivity measurments as functions of temperature at const ant de electric field and as functions of the de electric field at con stant temperatures in the paraelectric phase have been performed for D MAGaS crystal. The changes of the permittivity maximum with the electr ic field intensity evidence the first-order character of the ferroelec tric phase transition at T-cl The field dependence of the permittivity epsilon(E) in the paraelectric phase is discussed, using the classica l electric equation of state. A method for the determination of the co rresponding coefficients is proposed. The obtained B and C coefficient s, together with double hysteresis loop observed above T-cl prove the first-order character of the ferroelectric phase transition in DMAGaS crystal.