Relaxation effects in HTc-Superconducting Thin Films

Mechanical relaxation experiments have been widely applied to bulk high temperature (HT,) superconducting materials. In contrast to that only few results obtained on HT, superconducting thin films were reported. None dealt with stress driven phenomena due to the high background damping from the substrate materials used. In applied magnetic fields, however, a host reed technique can be used and the measured damping then gives information about the superconducting properties of the sample. We will discuss some experimental aspects and describe the basic information which was obtained on YBa2Cu307, and Bi2SrzCaC~208+x thin films. This includes the lower critical field, the Labusch parameter, pinning energies related to the model of thermally assisted flux flow (TAFF), and a matching effect of the flux line lattice (FLL) to the thickness of the films.