Phase transitions in C_2O_4HNH_4, 1/2 H_2O. A light scattering study at normal pressure - Université Pierre et Marie Curie Accéder directement au contenu
Article Dans Une Revue Journal de Physique Année : 1987

Phase transitions in C_2O_4HNH_4, 1/2 H_2O. A light scattering study at normal pressure

Résumé

C_2O_4HNH_4, 1/2 H_2O undergoes, at Tc = 145 K, a second order ferroelastic transition. The present Raman study allows us to identify the soft degree of freedom responsible for the transition as the ordering of one family of NH4+ ions. This ordering process appears as a central peak which displays a critical narrowing in the vicinity of Tc. Nevertheless, its linewidth is minimum not at Tc but below Tc. The combined analysis of its intensity and linewidth shows that this unusual behaviour is due to the evolution of the individual ionic relaxation time. The latter is strongly modified, below Tc, by the inequivalence between the two potential wells, as well as by the change of the potential barrier. This model gives quantitative agreement with our results.

Dates et versions

hal-04084550 , version 1 (28-04-2023)

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Citer

Jean-Luc Godet, M. Krauzman, J.P. Mathieu, H. Poulet, N. Toupry. Phase transitions in C_2O_4HNH_4, 1/2 H_2O. A light scattering study at normal pressure. Journal de Physique, 1987, 48 (5), pp.809-819. ⟨10.1051/jphys:01987004805080900⟩. ⟨hal-04084550⟩
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