Pressure dependence of electron-phonon coupling inCe3+-dopedGd3Sc2Al3O12garnet crystals

Abstract

Spectroscopic properties of ${\mathrm{Ce}}^{3+}$ in ${\mathrm{Gd}}_{3}{\mathrm{Sc}}_{2}{\mathrm{Al}}_{3}{\mathrm{O}}_{12}$ have been investigated by high-pressure luminescence and absorption spectroscopy up to 200 kbar. The emission and absorption bands originating from $5d\ensuremath{\leftrightarrow}4f$ transitions were observed to shift to red with pressure at a rate of $\ensuremath{-}7.9{\mathrm{cm}}^{\ensuremath{-}1}/\mathrm{kbar}$ and $\ensuremath{-}15.2{\mathrm{cm}}^{\ensuremath{-}1}/\mathrm{kbar},$ respectively. A large difference in the pressure-induced shifts indicates a large decrease in the electron-lattice coupling strength. Using the standard crystal-field approach and configurational coordinate model, quantitative descriptions of the effect of pressure on the energy, band shape, and electron-phonon coupling have been conducted. We have found that the local compression of a $[{\mathrm{CeO}}_{8}{]}^{13\ensuremath{-}}$ complex in ${\mathrm{Gd}}_{3}{\mathrm{Sc}}_{2}{\mathrm{Al}}_{3}{\mathrm{O}}_{12}:{\mathrm{Ce}}^{3+}$ is about two times smaller than that of bulk material. We have also estimated the local Gr\"uneisen parameter for ${\mathrm{Gd}}_{3}{\mathrm{Sc}}_{2}{\mathrm{Al}}_{3}{\mathrm{O}}_{12}:{\mathrm{Ce}}^{3+}$ system to be about 2.66.