Relaxor Ferroelectrics—From Random Field Models to Domain State Physics

Abstract

Substitutional charge disorder in ferroelectrics giving rise to quenched electric random-fields (RFs) is probably at the origin of their relaxor behavior. Fluctuating polar nanoregions in the paraelectric regime are related to the spatial fluctuations of the RFs. While they destroy the ferroelectric phase transition and give rise to a glassy state in cubic relaxors like PbMg_⅓Nb_2/3O₃, uniaxial systems like Sr_1-x Ba _x Nb₂O₆ exhibit RF Ising model behavior with non-classical critical exponents, e.g. α ≈ 0. Metastable pinned nanodomains in the ferroelectric regime are at the origin of non-Debye dielectric response, non-exponential relaxation, aging and memory effects.

Keywords:

• Relaxor ferroelectric
• random fields
• susceptibility
• domains
• relaxation
• aging

Acknowledgments

Financial support by DAAD, DFG (SPP “Strukturgradienten in Kristallen”) and NATO (PST.CLG.977409) is gratefully acknowledged.