Dresden 2003 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 8: Supraleitung: Dünne Schichten, Josephsonkontakte, SQUIDs
TT 8.9: Vortrag
Dienstag, 25. März 2003, 11:45–12:00, HSZ304
Microwave Properties of epitaxial Y1−xCaxBa2Cu3O7−δ films — •Ermile Gaganidze1, Roland Heidinger1, Juergen Halbritter1, Michael Lorenz2, and Holger Hochmuth2 — 1Forschungszentrum Karlsruhe, Institut fuer Materialforschung I, Postfach 3640, 76021 Karlsruhe, Germany — 2Universitaet Leipzig, Fakultaet fuer Physik und Geowissenschaften, Institut fuer Experimentelle Physik II, Linnestr. 5, 04103 Leipzig, Germany
Ca (≤ 22 at %) substituting Y in
YBa2Cu3O7−δ (YBCO) is well known
to enhance the in-plane conductivity σ (T>Tc) and
density of states nm and to enhance the critical current
density jcJ(T<Tc) of bycristal boundaries. However, up to
now no data are available on microwave properties of epitaxial
Ca-doped YBCO films.
Here first results are presented on large area PLD grown
Y1−xCaxBa2Cu3O7−δ (Y1−xCaxBCO)
films on 3-inch r-cut sapphire wafer with a CeO2 buffer
layer. The microwave surface resistance Rs(T,Hrf) at 8.5
GHz of Ca substituted Y0.9Ca0.1BCO shows clear reductions
with respect to that of YBCO for temperatures below about 50 K
up to the fields of 20 mT. Systematic studies and analysis of
Rs(T<Tc,Hrf) of 170 nm thin Y1−xCaxBCO films
with x =0; 0.1; 0.15 and 0.2 are presented. The separation of
Rs in intrinsic Rint and extrinsic rf residual losses
Rres(T,Hrf) and their field dependencies reveals a
reduced mean free path l(T) due to weak scattering at Ca in
Rint(T), and an enforced strength jcJ of natural weak
links explainable by an enhanced nm by additional hole doping
by Ca.