Sound velocities of YBa2Cu3O7−δ single crystals measured by Brillouin spectroscopy

Abstract The sound velocities of YBa 2 Cu 3 O 7− δ single crystals have been measured at 300 K by means of Brillouin light scattering. The Rayleigh surface mode and the surface resonance of the longitudinal acoustic phonon mode have been observed for wave vectors perpendicular as well as parallel to the crystallographic c-axis. From the measured sound velocities the elastic constants C 11 = 211±15 GPa and C 33 = 159±12 GPa are determined and an estimate of 44 (33–36 GPa) is given. A 25% anisotropy is found for the longitudinal elastic modes perpendicular and parallel to the (a,b)-plane. No significant deviations of the sound velocities from the room temperature values are found at 80 K and 11 K.