Europhys. Lett.
Volume 66, Number 4, May 2004
Page(s) 520 - 526
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 May 2004
Europhys. Lett., 66 (4) , pp. 520-526 (2004)
DOI: 10.1209/epl/i2004-10016-x

Aging of the asymmetry induced by the biasing electric field in a disordered ferroelectric

B. Bonello, P. Doussineau, V. Dupuis and A. Levelut

Laboratoire des Milieux Désordonnés et Hétérogènes (UMR CNRS 7603), Université Pierre et Marie Curie (case 86) 75252 Paris cedex 05, France

(Received 5 January 2004; accepted in final form 8 March 2004)

Isothermal aging of the disordered dielectric crystal $\chem{KTa}$ 1-x $\chem{Nb}$ x $\chem{O_3}$ ( x=0.027), the symmetry of which is broken by the biasing electric field E, is studied by means of AC dielectric-constant measurements. The asymmetry of the crystal induced by the field is put in evidence by the response of the dielectric constant to the small field change $\delta\bm{E}$. This response contains an anisotropic contribution proportional to $\delta E$ and an isotropic positive contribution proportional to $(\delta E)^2$. The former slowly decreases whereas the latter increases as time elapses. Our results are well interpreted in the framework of a model which attributes the time-dependent part of the dielectric constant to the evolution of the polarization domain walls: the slow decrease (aging) of the linear contribution is related to the decrease of the total wall area, which is a consequence of the domain growth, while the fast increase (rejuvenation) of the quadratic contribution is the signature of wall reconformations.

61.43.-j - Disordered solids.
77.22.Gm - Dielectric loss and relaxation.

© EDP Sciences 2004