Polarization relaxation in (CH3NH3)5Bi2Br11 ferroelectric crystals

Abstract

The time-dependent relaxation of retained polarization in unipolar methylammonium bromobismuthate, (CH 3 NH 3 ) 5 Bi 2 Br 11 , single crystal was examined by optical observation of the domain structure. The polarization relaxation is attributed to the presence of a built-in internal bias field caused by structured disorder in the crystal. The internal field accounts for the broad spectrum of potential barriers for the domain walls. The slow polarization decay, in the long-time regime (t > 1 s), follows a stretched exponential and/or power-law function. On the assumption that relaxation centers (domains) are noninteracting, a distribution function of relaxation times is reconstructed.

Effect of internal bias field on domain switching in (CH3NH3)5Bi2Br11 crystal

“…Such a field caused by structural disorder in the MAPBB crystal accounts for the broad spectrum of potential barriers for domain walls. 28 This may be confirmed by a spatially nonuniform distribution of domain nuclei induced by E b during backswitching process. The results indicate that no significant difference exists in the polarization relaxation behavior of bulk material and that observed in thin films.…”