Münster 1999 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Tiefe Temperaturen
TT 16: Anwendungen der HTSL: Hochfrequenz und Elektronik
TT 16.3: Vortrag
Donnerstag, 25. März 1999, 11:00–11:15, F1
Cavity perturbation by superconducting films in microwave magnetic and electric fields — •D.-N. Peligrad1, B. Nebendahl1, A. Dulčić2, and M. Mehring1 — 1Universit"at Stuttgart, 2. Physikalisches Institut, D-70550 Stuttgart — 2Department of Physics, Faculty of Science and Ruder Bošković Institute, POB 162, HR-10001 Zagreb, Croatia
Cavity perturbation by superconducting films is treated in an unified way for the sample positions in both magnetic and electric microwave fields. The role of demagnetizing and depolarizing effects in the boundary conditions of the fields is analyzed. The general solutions for the complex frequency shift are specified for the samples having slab geometry and the field being parallel to the plane of the sample. For electromagnetically thick samples, the shifts for samples placed in the magnetic and electric fields are found to have the same magnitude and temperature dependence, while for thin films dramatic differences are obtained. The magnitude of the shift is reduced in the magnetic and increased by orders of magnitude in the electric field. A remarkable feature in the temperature dependence of the real frequency shift in the electric field is obtained. Experiments are performed on an YBa2Cu3O7−δ thin film, and all the predictions of the theory are confirmed. It is also shown that microwave cavity perturbation and ac susceptibility measurements in a dc magnetic field can be covered by the same theory.