Thin Superconducting Film Characterization by Surface Acoustic Waves.
Abstract
Both the dc electrical resistivity and the attenuation of surface acoustic waves (SAW) were measured in the superconducting state of a granular lead film as a function of an applied magnetic field normal to the film plane. At 4.2 K the data appear to yield an upper critical of about 60 K Gauss and a lower critical field of about 20 K Gauss. A theoretical model that takes into account renormalization has been developed for explaining the SAW attenuation in a superconducting NbN film with a sheet resistivity of 30 k ohms/sq. Bulk ultrasonic measurements in the ferromagnetic superconductors Er(x)Ho(1-x)Rh4B4 indicate that spin phonon interaction increases in the superconducting state of these ternary compounds. Ultrasonic measurements in very pure vanadium single crystals provide low temperature data which yield a zero temperature energy gap 2 Delta(0) that is very close to the BCS value of 3.5 kT sub c but the data close to the superconducting transition temperature T sub c would yield 2 Delta (0) = 4.2 kT sub c. A theoretical model is being investigated to ascertain if it will resolve this apparent discrepancy.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 22, 1985
- Accession Number
- ADA158311
Entities
People
- M. Levy
Organizations
- University of Wisconsin Madison Department of Physics