Abstract
In this paper we present the results of a study of the effects of dynamical fractality on vibrational dynamics and electron-vibration coupling in AgI-doped borate glasses, namely the compounds (AgI)x(Ag2O-nB2O3)l-x, with n=1 and x = 0.4, 055 and 0.65. The samples were studied by time-of-flight inelastic neutron scattering and by Raman scattering at several temperatures. Particular care was given to obtain a precise and reliable spectral density with both techniques in the low-frequency range, namely about 1 to about 8O cm−1. In this range, clear indications of fractality were obtained from the anomalous behaviour of the vibrational density g N(ω) of states obtained by neutron scattering. In the same region we also observed a scaling behaviour of the electron-vibration coupling function, obtained from the ratio of the Raman spectral density g R(ω) to the neutron spectral density. g N(ω) was found to be essentially independent of temperature, whereas g N(ω) featured significant changes in the region ω≈100cm−1 and for ω≈10 cm−1, as the temperature was varied between 100 and 288 K. The changes indicate a modification of the spectral dependence of electron-vibration coupling due to activation of Ag ion motion in the dynamically fractal structure of AgI dissolved in the borate matrix.