Thin Superconducting Film Characterization by Surface Acoustic Waves

摘要

A dilution refrigerator was installed tested and modified. Several cryogenic probes were fabricated to measure resistivity, ac susceptibility and ultrasonic attenuation in high T superconductors. Ultrasonic attenuation measurements were performed on single crystals of UPt3 and URu2Si2. A maximum in attenuation was found below the superconducting transition temperature TC of URu2Si2. A magnetic field decreased this maximum. The temperature of the attenuation in the normal and superconducting states below Tc was measured in UPt3. The ratio of the attenuation follows a power law dependence indicative of an anisotropic superconducting energy gap. A peak in attenuation was found in the mixed state of UPt3, which may be associated with a phase transition of the flux line lattice.