SPECIFIC-HEAT AND LOW-ENERGY EXCITATIONS OF SAMARIUM PHOSPHATE-GLASSES

The specific heats of (Sm2O3)(0.19)(P2O5)(0.81) and (Sm2O3)(0.25)(P2O5)(0.75) glasses have been measured between 1.5 and 30 K using a calorimeter based on the thermal relaxation method. The results show an additional specific heat over that predicted from the Debye theory, which has been interpreted in terms of an excess of localized vibrational modes. To provide a basis for preliminary data analysis in terms of localized states, a phonon-fracton density of states has been used. The fit to the excess specific heat gives model parameters having the same magnitudes as those found previously for a wide range of glasses. The cross-over temperature from phonon to fracton behaviour estimated from the excess specific heat is similar to that obtained from recent low-frequency Raman scattering measurements.