Low-temperature specific heats of lanthanum and yttrium phosphate glasses |
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Authors: | G Carini G D'Angelo G Tripodo G A Saunders |
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Institution: | (1) Dipartimento di Fisica dell'Università Contrada Papardo, Salita Sperone 31, 98166 S. Agata, Messina, Italy;(2) School of Physics, University of Bath, Claverton Down, Bath, UK |
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Abstract: | Summary The specific heats of (R2O3)
x
(P2O5)1−x
glasses containing high concentrations of La3+ and Y3+ ions have been measured between 1.5K and 30K. It is shown that, in addition to the usual Debye contribution, there is an
excess specific heat arising from localized vibrational states which has been discussed in terms of two distinct models. The
first predicts a maximum in the temperature dependence of the excess specific heat associated with the crossover frequency
from phonon to fracton behaviour. The phonon-fracton density of states used to fit the excess specific heat gives rise to
model parameters having the same magnitudes as those found previously for other glasses including samarium phosphates. The
second model, formulated on the basis of soft vibrations in glasses, predicts a minimum in the excess specific heat, which
is also observed.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Capanello, Italy, July 4–8, 1994. |
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Keywords: | Vibrational states in disordered systems |
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