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 calori meter based on the thermal relaxation method. The results show an addi tional specific heat over that predicted from the Debye theory, which has been interpreted in terms of an excess of localized vibrational mo des. To provide a basis for preliminary data analysis in terms of loca lized states, a phonon-fracton density of states has been used. The fi t to the excess specific heat gives model parameters having the same m agnitudes as those found previously for a wide range of glasses. The c ross-over temperature from phonon to fracton behaviour estimated from the excess specific heat is similar to that obtained from recent low-f requency Raman scattering measurements.