Pyrochlore 'dynamic spin-ice' Pr2Sn2O7 and monoclinic Pr2Ti2O7: A comparative temperature-dependent Raman study

Here we report a temperature-dependent Raman study of the pyrochlore 'dynamic spin-ice' compound Pr2Sn2O7 and compare the results with its non-pyrochlore (monoclinic) counterpart Pr2Ti2O7. In addition to phonon modes, we observe two bands associated with electronic Raman scattering involving crystal field transitions in Pr2Sn2O7 at ∼135 and 460 cm-1 which couple strongly to phonons. Anomalous temperature dependence of phonon frequencies that are observed in pyrochlore Pr2Sn2O7 are absent in monoclinic Pr2Ti2O7. This, therefore, confirms that the strong phonon-phonon anharmonic interactions, responsible for the temperature-dependent anomalous behavior of phonons, arise due to the inherent vacant sites in the pyrochlore structure. - Abstract: The phonon-phonon anharmonic interaction which is responsible for the temperature-dependent anomalous behavior of phonons, arise due to the inherent vacant sites in the pyrochlore structure. Highlights: → Pyrochlore Pr2Sn2O7 and its monoclinic counterpart Pr2Ti2O7 are compared. → Raman spectroscopic data reveal temperature-dependent phonon anomalies. → Crystal field transitions in Pr2Sn2O7 couple with phonons. → Phonon anomalies are attributed to phonon-phonon anharmonic interactions. → Phonon anharmonicity in pyrochlores arise due to their inherent vacancies.