Correlated domain dynamics in relaxor ferroelectrics and random-field systems

Abstract

The dielectric response of the relaxor ferroelectrics PbMg_1/3Nb_2/3O₃ and Sr_0.998Ca_0.002TiO₃ is measured via the complex permittivity, ε(ω), and the relaxation of the field-cooled polarization in zero-field, P(t), respectively. Its polydispersivity is attributed to dynamically correlated domains with percolation size distribution. They are induced by spatial fluctuations of intrinsic quenched random-fields. Whereas activated dynamics prevails above T _c, non-activated domain wall dynamics occurs below T _c. This contrasts with the activated random-bond controlled ordering kinetics of field-induced domains in the diluted two-dimensional Ising antiferromagnet Rb₂Co_0.85Mg_0.15F₄.

Key Words:

• Dielectric permittivity
• Polarization
• Relaxation
• Random-fields
• Polar domains
• Antiferromagnetic domains
• Second-harmonic generation