Title :
Microwave losses of YBCO thin films in high magnetic fields
Author :
Ghosh, I.S. ; Cohen, L.F. ; Fry, V. ; Tate, T. ; Caplin, A.D. ; Gallop, J.C. ; Sievers, S. ; Somekh, R. ; Hensen, S. ; Lenkens, M.
Author_Institution :
Imperial Coll. of Sci., Technol. & Med., London, UK
fDate :
6/1/1995 12:00:00 AM
Abstract :
A parallel plate resonator technique was employed to investigate changes in the microwave surface impedance between 20 K and 60 K, when d.c. magnetic fields up to 4 T were applied parallel to the YBCO film surface. By using a simple model to describe the observed behaviour, we can extract values for the vortex viscosity /spl eta/ and pinning constant /spl kappa//sub p/, as a function of temperature in three sets of films. As a result of low energy deuterium ion implantation in one of the films, the low field behaviour was degraded but at high fields the pinning properties improved quite drastically. A much smaller effect was observed in field dependence of the dc screening current as measured using vibrating sample magnetometry.<>
Keywords :
barium compounds; flux flow; flux pinning; high-frequency effects; high-temperature superconductors; ion implantation; losses; superconducting thin films; surface conductivity; yttrium compounds; 0 to 4 T; 20 to 60 K; 5.3 GHz; 5.4 GHz; DC screening current; YBa/sub 2/Cu/sub 3/O/sub 7/; YBaCuO thin films; high magnetic fields; low energy D ion implantation; microwave losses; microwave surface impedance; parallel plate resonator technique; pinning constant; vibrating sample magnetometry; vortex viscosity; Deuterium; Ion implantation; Magnetic fields; Magnetic films; Microwave theory and techniques; Surface impedance; Temperature; Time of arrival estimation; Viscosity; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
