Low-temperature specific heat in caesium borate glasses
Résumé
Low temperature specific heat measurements (1.5-25 K) performed on caesium borate glasses at different concentrations have pointed out the presence of an excess specific heat Cp over the Debye contribution. In a plot Cp/T3 vs. T it appears as a bump whose temperature location is almost unchanged while its intensity increases with caesium concentration. A comparison with the specific heat in sodium borate glasses has revealed highly dissimilar low energy dynamics, despite of the same structural units building up the borate matrix. The different behaviors observed have been related to the peculiar structural changes that the inclusion of alkaline cations cause in the mesoscopic length scale where the effects of the medium range order (MRO) are usually observed. It is believed that the particularly open structure of caesium glasses assures a very low frequency to the local oscillations of Cs+ ions that, consequently, rule with their localized character the vibrational dynamics in the frequency region of the Boson peak.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...