T.S. Velichkina

New data concerning surface Mandelstamm-Brillouin light scattering from the basal plane of germanium crystal

Abstract The intensity of Mandelstamm-Brillouin satellites (MBS) corresponding to leaky surface waves (LSW) was rigistered for Ge crystal of z -cut. The intensity was found to reach its largest values for two orientations of the light scattering plane: first, when the plane was parallel to [110], and second, when parallel to [cos 35°, sin 35°, 0]. A broad additional surface spectral line located at a frequency ≈ 1.4 times higher than those of MBS related to generalized surface waves and LSW was detected.

Mandelstamm-Brillouin studies of peculiarities of the phonon frequency distribution at cubic crystal (001) surfaces

Abstract For z -cut cubic crystals of Si, GaAs, InSb measurements of the peak intensities of Mandelstamm-Brillouin satellites corresponding to surface excitations of the pseudo surface mode (PSM) frequency range were conducted. The angular intensity dependence for various plane of incidence orientations reveal two maxima, for θ 2 =45°, and for θ 2 =36° ( Si ), 33° (GaAs), and 32° (InSb). Here θ is the angle between the (010) plane and the plane of incidence of light. The variations of the PSM satellite linewidth registered experimentally for the first time demonstrate the positions of its minima to be well correlated with θ 1,2 in all the cases. The non-monotonous peak intensity and the linewidth of the PSM satellite behavior are explained by PSM attenuation anomalies around θ 1,2 .

Observation of surface Mandelstamm-Brillouin light scattering spectra in high-temperature superconducting YBa2Cu3O7-° and La2-xSrxCuO4-δ single crystals and surface wave velocity determination

Abstract Observations of light scattering spectra caused by thermally excited surface Rayleigh waves in YBa2Cu3O7-δ and La2-xSrxCuO4-δ high Tc superconducting single crystals are reported. Surface wave velocities are obtained from the Brillouin line frequency shifts at room temperature.

Surface Mandelstamm-Brillouin light scattering from basal plane of germanium crystal

Abstract Mandelstamm-Brillouin (MB) surface light scattering spectra of z-cut cubic crystal of Ge are experimentally studied. Simultaneous observations of MB satellites caused by generalized surface waves and pseudo-surface “leaky” waves are reported.

Anisotropy of Rayleigh wave velocity of TmBa2Cu3O7−y single crystals

Abstract The Rayleigh waves velocities and their anisotropy were studied in both untwinned, twinned TmBa 2 Cu 3 O 7−y orthorhombic crystals and in tetragonal ones. The experiments were performed at room temperature.

Determination of rayleigh wave velocities in high Tc superconducting RBa2Cu3O7−y (R = Nd, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm, Yb) single crystals by Mandelstamm-Brillouin light scattering spectra

Abstract We obtained Rayleigh wave velocities in rare earth cuprate crystals in both orthorhombic and tetragonal phases at room temperature. Rayleigh wave velocity in superconducting samples was shown to be varied from 2.1 to 2.3 km/s in connection with cation R radius. The annealing of the crystals under oxygen flow at 450 °C produced 3–6% velocity increase. Tetragonal samples velocity values were found to be 10–15% lower the ones in orthorhombic modified crystals.

Bi-based superconductors and their surface wave velocities

Abstract We have measured the surface hypersound velocity values VR of Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 single crystals by Mandelstamm-Brillouin light scattering spectra. Measurements were performed at room temperature. In case of Bi2Sr2CaCu2O8 crystal considerable difference (20%) of (001) plane VR values along a and b crystallographic directions was manifested. However mentioned VR anisotropy in Bi2Sr2CuO6 crystals was not observed.

Mandelstamm-Brillouin studies of light scattered by (110) faces of GaAs, InSb and PbS crystals

Abstract Mandelstamm-Brillouin (MB) surface light-scattering spectra of (110)-cut GaAs, InSb, and PbS crystals were studied and surface wave velocities were determined for various θ (110) values; θ (110) is the angle between the [001] direction and the plane of the incident light. Both GaAs and InSb crystals demonstrated a considerable GSW high-frequency one-sided line broadening for θ (110) =40°–45°. Observations made for a PbS crystal revealed a GSW-pseudo surface mode (PSM) transition at θ (110) =70°–80 °.

Determination of high-frequency pseudo surface mode velocity in high-Tc superconducting RBa2Cu3O7−y (R= Tm, Er, Ho, Dy, Gd, Eu, Sm, Nd, Pr) single crystal by Mandelstamm-Brillouin light scattering spectra

Abstract The registration of Mandelstamm-Brillouin spectral lines corresponding to High Frequency Pseudo Surface Mode (HFPSM) and consequent VHFPSM velocity determination in both orthorhombic and tetragonal structured RBa2Cu3O7−y crystal is reported. For orthorhombic crystal VHFPSM drops from 5.8 to 5.2 km/s with the incrase of R element ionic radius from R= Tm to Pr, and VHFPSM values measured in non-superconducting tetragonal structured crystals are 5–6% lower than in more oxygen saturated orthorhombicc crystals. Similar dependencies from the crystals nature may be assumed also to corresponding bulk longitudinal velocity values.

Hypersound studies of the electron doped Ln2−xCexCuO4 and hole doped La2−xMxCuO4 high-Tc single crystals

Abstract Here we report the growth of the electron doped HTSC Ln 2− x Ce x CuO 4 ( Ln = Gd , Eu , Nd , Pr ; x =0, 0.15) single crystals and room temperature measurements of their hypersound surface acoustic wave (SAW) velocities V SAW . Mandelstamm-Brillouin light scattering was used to the determination of the V SAW values in (001) crystal planes. SAW velocities of the hole doped La 2− x M x CuO 4 ( M = Ca , Sr , Ba ; 0 ⩽ x ⩽ 0.15) crystals were also measured. For both type of crystals V SAW is constant for all the azimuths of the SAW vector in the (001) plane. In the case of Ln 2−x Ce x CuO 4 crystals the V SAW value rises ≈20% with the Ln radii increase from Gd to Pr.