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

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: 8 March 2004

Abstract

Isothermal aging of the disordered dielectric crystal _x (), the symmetry of which is broken by the biasing electric field , 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 . This response contains an anisotropic contribution proportional to and an isotropic positive contribution proportional to . 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.