The pressure response of Raman active phonon modes of Tm₃Al₅O₁₂

Abstract

We present the Raman spectrum of Tm₃Al₅O₁₂ single crystal and its pressure dependence for hydrostatic pressure up to 11GPa and room temperature. Tm₃Al₅O₁₂ belongs to the crystal family of rare earth garnets (Re₃A1₂(AlO₄)₃, Re: Gd, Tb, Dy, Er,…), which crystallize in the body-centered cubic lattice and contains eight molecular units in the conventional unit cell, Group theory predicts 25 Raman active modes for these compounds, while experimentally are observed 15 modes. As crystal volume decreases all Raman peaks exhibit pressure coefficients varying from 0.7 to 5.6cm⁻¹/ GPa. A large part of the vibrational spectra of these compounds could be explained taking into account the vibrational properties of molecular subunits, namely AlO₄.

Key Words:

• Garnets
• Raman scattering
• Phonons
• High pressure