Elastic Constants of Single-Crystal Rare-Earth Bismuth Iron Garnet Films

Abstract

Complete sets of elastic constants of rare-earth bismuth iron garnet (111) films containing Pb were determined by resonant-ultrasound spectroscopy. Resonant-ultrasound spectroscopy can be used to determine all independent elastic constants from one specimen by measuring the resonance frequencies of free vibrations. For accurate measurement of the resonance frequencies, we used a tripod transducer, and the vibration modes of each resonance frequency were identified by laser-Doppler interferometry. Rare-earth bismuth–iron garnet belongs to the space group Ia3d, and shows cubic symmetry. However, it was nearly elastically isotropic; 2C44/(C11 - C12) = 0.99. Their elastic constants were almost independent of the Pb content; C11 = 242.9 ±4.4 GPa, C12 = 99.1 ±2.0 GPa, and C44 = 71.1 ±0.8 GPa. The observed isotropic elasticity corresponds to that of the other garnet group crystals.