Relaxations, low-energy excitations and specific heat in phosphate glasses

Abstract

Abstract We have obtained low-frequency Raman spectra of samarium phosphate glasses (Sm2O3) x (P2O5)]1-x in a wide temperature range from 11 K up to the glass transition temperature (T g ≈ 910 K) and measured their low-temperature specific heat, in an attempt to test the predictions of some recent models, the soft-potential (SP) model and the mode-coupling (MC) model, addressing low-energy modes in glasses. The temperature and frequency dependence of the boson peak (BP) and the quasielastic scattering (QS), both features characteristic of glasses in the low-frequency range, were determined. In addition, at high temperatures (above 600 K) we have detected a strong structureless background, which is attributed to higher-order Raman scattering. Taking the background into account, the BP changes with temperature in accordance with the Bose-Einstein population factor over the investigated temperature range. The temperature dependence of the QS is found to be consistent with the suggestions of the SP and MC mod...