The cluster glass route of relaxor ferroelectrics

Abstract

Relaxor ferroelectrics such as PbMg_1/3Nb_2/3O₃ (PMN), Sr_0.75Ba_0.25Nb₂O₆ (SBN75) and BaTi_0.65Zr_0.35O₃ (BTZ35) are disordered ferroelectric solids, in which polar nanoregions (PNRs) are stabilized on cooling by random electric fields due to either charge or structural disorder prior to their cluster glass transitions at T_g. This two-step process is clearly distinct from conventional (atomic) spin glass transitions. Decisive features of the mesoscopic cluster glass ground states are critical glass dynamics at T_g and stretched exponential relaxation, memory and rejuvenation upon aging below T_g.

Keywords:

• relaxors
• random fields
• polar nanoregions
• glass transition
• aging

Acknowledgments

Fruitful discussions with S.A. Prosandeev, D. Sherrington and V.V. Shvartsman are gratefully acknowledged.