Brillouin Scattering Investigation of Glass-Like Properties in (KBr)1-x(KCN)x Mixed Crystals

Abstract

<p> Brillouin scattering technique is used to investigate the transverse acoustic phonon in (KBr)1-x(KCN)x alloy as a function of temperature for CN- concentration ranging from 0.20 to 0.50. Anomalies in phonon frequency and linewidth are observed and discussed in terms of coupling of the acoustic phonons with orientational motion of CN- ions based on a dynamic microscopic model suggested by Michel et al. The frequency and concentration dependence of the freezing temperature, which marks the formation of an orientational glass state, is examined.</p> <p> A high resolution tandem Fabry-Perot interferometer yields the first evidence of a complex spectrum which consists of the phonon peak and new equal-spaced modes. The Bayesian deconvolution technique is used to extract the spectra. The concentration, time and temperature dependence of these new modes are presented. It is proposed that they arise from the modification of the tunneling levels of the CN, and appear to have the uniform density of states which is the characteristic property of the glass.</p>