Ivan A. Yakovlev

Optical examination of inhomogeneities of quartz crystals in the vicinity of the phase transition

Abstract It is found that some state of monocrystal of quartz exists in a narrow temperature range in the vicinity of the α-β transition which is characterized by sharp stationary inhomogeneities of the refraction index. Inhomogeneities represent “columns” with a mean cross section of 20–30 mkm elongated along the optical axis of the crystal. The modulation range of the refraction index varies from sample to sample and amounts to (0.7–1.5) × 10−5.

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.

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.

A SYSTEMATIC STUDY OF THE SURFACE WAVES OF HIGH-T c SYPERCONDUCTING SINGLE CRYSTALS

Hypersound surface wave propagation in case of RBa2Cu3O7-y-family crystals, Bi-based superconductors, and electron and hole doped rare earth cuprates was studied by Mandelstamm-Brillouin spectroscopy.