Nontrivial dependence of dielectric stiffness on bias field in relaxors and dipole glasses

Abstract

Dielectric permittivity and Second Harmonic Generation (SHG) studies in the field-cooled mode show a linear dependence of dielectric stiffness (inverse dielectric permittivity) on dc bias in PMN-PT crystals and SHG intensity in KTaO3:Li at small Li concentrations. We explain this unusual result in the framework of a theory of transverse, hydrodynamic-type, instability of local polarization.

Peculiarities of temperature and field dependence of tunability in Ba0.6Sr0.4TiO3 ceramics with differing grain sizes

“…Usually, the surface effect in ferroelectric ceramics is related to the deadlayer [1,10], but, it follows from our observation that, in reality, the dead layer is a result of the action of the random fields with the source in the inter-crystallite interface. Thus, indirectly, our data are supported by the theories of tunability of small-crystallite-size ceramics employing the idea of the dead layer [10,11].…”

Bias-field effect on the temperature anomalies of dielectric permittivity inPbMg1∕3Nb2∕3

“…Details of dielectric studies have been described elsewhere. 5,7 The majority of our experimental data have been obtained in the 1 -100 kHz frequency range. It is well documented in the literature that, in the case of the PMN-PT compositions, this range is wide enough to demonstrate the frequency dispersion of permittivity and the frequency shift of T m .…”

“…In relaxors, such a dependence has also been observed above some threshold field, and it was explained by the divergence of the transverse susceptibility. 7 Poplavko 39 assumed that the average relaxation time in relaxors decreases with the increase of bias field. Tagantsev and Glazounov 38 suggested that the vibration of PNR's can be described by the following field dependence of the relaxation time: = 0 exp͓͑U − VPE͒ / k B T͔ where V is the PNR's volume and P the polarization magnitude inside PNR's.…”

“…Such a supposition is also supported by the character of the field dependence of permittivity in ͓111͔ PMN crystals. 7 This phase transition was modeled by Vugmeister and Rabitz 14 by considering the average polarization as a function of field in the spirit of the Landau mean-field theory. Pirc, Blinc, and Kutnjak 15 modeled a similar phase diagram obtained for Pb 1−y La y Zr 1−x Ti x O 3 ͑PLZT͒ within the spherical randombond random-field ͑SRBRF͒ model supplemented with a field modulation of intercluster coupling.…”

“…[1][2][3][4][5][6][7][8][9][10] Besides, they serve as model objects for studying relaxor properties. Relaxors represent a class of disordered crystals exhibiting a broad and frequency-dependent temperature maximum of the dielectric permittivity versus temperature instead of a sharp maximum inherent to normal ferroelectrics.…”