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In a thin film of superconducting YBCO the impact of surface acoustic waves (SAWs) traveling on the piezoelectric substrate is investigated. A pronounced interaction between the ultrasonic waves and the vortex system in the type II superconductor is observed. The occurrence of a SAW-induced dc voltage perpendicular to the sound path is interpreted as {\em dynamic pinning} of vortices by the piezoacoustic SAW, which acts as a conveyor for the fluxquanta. Its antisymmetry with respect to the magnetic field directly evidences the induced, directed flux motion.This dynamic manipulation of vortices can be seen as an important step towards flux-based electronic devices.Comment: submitte

The precise determination of elastic constants of γ-LiAlO2 has recently become important, as this material is being used as a substrate for intensely studied acousto-optical device structures and no values for the elastic moduli have been published to date. The precision of experimentally determined elastic constants hinges significantly on considering the influence of the acoustic transducer on the sound propagation in the system. Therefore, the influence of the transducer is discussed and an approach for corrections is presented. The compressional elastic constants C11 and C33 and the shear constants C12 and C13 of γ-LiAlO2 are determined with an acoustic pulse-echo technique and with sampled-continuous-wave spectroscopy.

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The interaction of surface acoustic waves (SAW) with the magnetic vortex system in YBa2Cu3O7 is investigated. A 100nm YBCO film is deposited on a piezoelectric substrate and structured for electrical 4-point measurements. Interdigital transducers are fabricated on the same substrate. When applying an external magnetic field perpendicular to the film surface a SAW-induced dc-voltage perpendicular to the acoustic sound-path is observed. This is interpreted as consequence of directed dragging of vortices by the SAW induced dynamic pinning structure [1]. The piezoacoustic wave acts as a conveyor for mobile flux quanta. Additional ac-dc-conversion as result of the nonlinear current-voltage characteristics close to the superconducting transition temperature can be resolved and separated. In order to observe the sound-induced vortex motion directly, the flux distribution is analyzed magnetooptically. Magnetooptic imaging allows for time resolved analysis of flux distribution. Quantitative analysis of changes in the magnetization distribution when acoustic driving fields are applied is carried out. The influence of piezoacoustic waves on the pinning properties and sound-induced depinning is discussed. [1] F.