Relaxation times ofBP1−xBPIxmixed crystals: Atypical dipolar glass behavior of the average local potential asymmetry

Abstract

Dielectric susceptibility measurements in a wide frequency spectrum were used to obtain the distribution of the relaxation times of ${\mathrm{BP}}_{1\ensuremath{-}x}{\mathrm{BPI}}_{x}$ mixed crystals. The dipole freezing results in a broad distribution of the relaxation times. The parameters of the double-well potentials of the hydrogen bonds, the local polarization distribution function and glass order parameter have been extracted from the dielectric measurements. The microscopic parameters are in good agreement with magnetic resonance data. The average local potential asymmetry ${A}_{0}$ shows a behavior different from that of RADP. Dielectric spectroscopy gives the new and surprising result that the nonzero mean ${J}_{0}∕{k}_{B}$ of the random bond interaction is vanishing for very low temperatures. One can suspect that it is related to the transition into the low-temperature nonergodic glassy phase.