A comparative study of specific-heat and low-frequency Raman scattering at low temperatures of lanthanide metaphosphate glasses and pentaphosphate single crystals has revealed the presence of low-energy magnetic excitations. In an analogous manner to that found for vibrational modes, topological disorder softens the crystal field magnetic excitations, producing a broad band of low-energy states with a low-energy tail. A self-consistent data analysis using a broad Gaussian distribution of singlet-singlet excitations allows a complete interpretation in Pr glass, which exhibits strong magnetic effects in the temperature range explored. This distribution is used to evaluate the magnetic contribution to the specific heat; about one-fifth of the magnetic ions are characterised by singlet-singlet states with very low energies and contribute to the magnetic entropy.
Effect of glassy topological disorder on low-energy magnetic excitations
CARINI, Giuseppe;D'ANGELO, Giovanna;TRIPODO, Gaspare;
2000-01-01
Abstract
A comparative study of specific-heat and low-frequency Raman scattering at low temperatures of lanthanide metaphosphate glasses and pentaphosphate single crystals has revealed the presence of low-energy magnetic excitations. In an analogous manner to that found for vibrational modes, topological disorder softens the crystal field magnetic excitations, producing a broad band of low-energy states with a low-energy tail. A self-consistent data analysis using a broad Gaussian distribution of singlet-singlet excitations allows a complete interpretation in Pr glass, which exhibits strong magnetic effects in the temperature range explored. This distribution is used to evaluate the magnetic contribution to the specific heat; about one-fifth of the magnetic ions are characterised by singlet-singlet states with very low energies and contribute to the magnetic entropy.Pubblicazioni consigliate
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