INTERACTION BETWEEN MICROWAVES AND VORTICES - INFLUENCE OF HEAVY-ION-INDUCED DEFECTS

We report experimental results on the external static magnetic field d ependence of the kinetic inductance of YBaCuO microstrip resonators, t hrough microwave resonance frequency measurements. We interpret our da ta in terms of granularity to relate the resonance frequency variation s to grain-pinned vortices or grain-boundary vortices. In order to mod ify the pinning characteristics of the material, the YBaCuO films were irradiated with 70 MeV Cu-63 ions, which are able to produce amorphou s ionization tracks in this material. We have studied the influence of these columnar defects on the frequency shifts observed in the resona tor. The results show that columnar defects may act as very strong pin ning centers inside superconducting grains, but they have little effec ts on vortices trapped in intergranular regions.