Surface waves on the a, b and c faces of untwinned single crystals of YBa2C3O7-δ

Abstract Using Brillouin scattering we have measured the angular dependence of surface wave velocities on the three principal faces of untwinned single crystals of YBa 2 Cu 3 O 7−δ . The angular dependence of the velocities on each surface and a comparison between the three surfaces are in agreement with calculations based on available elastic constants. There is, however, an overall discrepancy between the absolute value of the calculated and measured velocities. We obtain the elastic constants C 44 , C 55 and C 66 and compare them with existing data. The temperature dependence, down to 20 K, is also reported for the surface velocities.