Comparative study of the magnetoresistivity of YBa2Cu3O7-δ and Bi2Sr2Ca Cu2O8+x epitaxial thin films in the fluktuation regime

F. Gollnik, H. C. Ri, A. Beck, R. Gross, P. Wagner, H. Adrian

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Abstract

We measured the magnetoresistivity of high quality, c-axis oriented epitaxial YBa2Cu3O7-δ 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 ξab and ξc, respectively, and the product of the mean free path l and the phase breaking time τφ 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, ξab = 13.8 A ̊, ξc = 3.1 A ̊, and (lτgf)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 ξab ≅ 24 to 30 Å. The very small coherence length in c-direction ξc ≤ 0.4 Å reflects the quasi 2-dimensional nature of this material.

Original languageEnglish
Pages (from-to)1933-1934
Number of pages2
JournalPhysica C: Superconductivity and its Applications
Volume235-240
Issue numberPART 3
DOIs
StatePublished - Dec 1994
Externally publishedYes

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