Inhaltszusammenfassung

We measured the magnetoresistivity of high quality, c-axis oriented epitaxial YBa2Cu3O7?? and Bi2Sr2Ca Cu2O8 x (BSCCO) thin films in the fluctuation regime above the critical temperature. The measurements have been performed in magnetic fields up to 12 Tesla applied parallel and perpendicular to the CuO2-planes. The experimental data was analysed in the framework of the Lawrence-Doniach model with the appropriate clean limit expressions for the Aslamazov-Larkin- and Maki-Thompson- fluctuation...We measured the magnetoresistivity of high quality, c-axis oriented epitaxial YBa2Cu3O7?? and Bi2Sr2Ca Cu2O8 x (BSCCO) thin films in the fluctuation regime above the critical temperature. The measurements have been performed in magnetic fields up to 12 Tesla applied parallel and perpendicular to the CuO2-planes. The experimental data was analysed in the framework of the Lawrence-Doniach model with the appropriate clean limit expressions for the Aslamazov-Larkin- and Maki-Thompson- fluctuation conductivities. Orbital as well as Zeeman contributions to the magnetoconductivity have been taken into account. With the thermodynamic critical temperature Tc, the coherence lengths parallel and perpendicular to the ab-plane ?ab and ?c, respectively, and the product of the mean free path l and the phase breaking time ?? as fitting parameters, good agreement between experiment and theory was found for YBCO, whereas for BSCCO no convincing fit could be obtained. Fitting the data for YBCO we obtained Tc = 90.2K, ?ab = 13.8Å, ?c = 3.1 Å, and (l?gf)100K 1.5 × 10?22sm. These values are close to those derived from measurements of the transport energy of magnetic flux lines via the Nernst effect at temperatures below Tc. For BSCCO we obtained Tc 90 K and ?ab 24 to 30 Å. The very small coherence length in c-direction ?c ? 0.4 Å reflects the quasi 2-dimensional nature of this material. » weiterlesen» einklappen

Autoren

Klassifikation

DFG Fachgebiet:
Physik der kondensierten Materie

DDC Sachgruppe:
Physik