Münster 1997 – scientific programme

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TT: Tiefe Temperaturen

TT 6: Postersitzung I: Mesoskopie(1-21), amorphe Metalle und Defektsysteme(22-29), Kryotechnik, Kernmagnetismus(30-37), festes N₂(38), Quantenflüssigkeiten und -kristalle(39-48), dünne supraleitende Filme(49-68), schwere Fermionen und Kondosysteme(69-92), Fullerene(93-94)

TT 6.59: Poster

Tuesday, March 18, 1997, 09:30–13:00, Z1

Critical currents and Micro-structure in epitaxial YBa₂Cu₃O_7−δ thin films — •J.C. Martínez¹, B. Dam², B. Stäuble-Pümpin², G. Doornbos², R. Surdeanu², U. Poppe³, and R. Griessen² — ¹Institut für Physik, Johannes Gutenberg Universität, 55099 Mainz — ²Physics Department, Vrije Universiteit - Amsterdam, 1081 HV Amsterdam, The Netherlands — ³Institut für Festkörperforschung, Forschungszentrum Jülich,D-52425 Jülich, Germany

Epitaxial YBa₂Cu₃O_7−δ films nucleate in single-crystalline c-axis oriented islands. In the Island boundaries we observe Anti-phase boundaries which correspond to a mismatch between the CuO₂ superconducting blocks of one third of the c-axis lattice parameter of YBa₂Cu₃O_7−δ (Y:123). The density of island boundaries can be measured by a careful analysis of the surface morphology using Atomic Force Microscopy (AFM) and Scanning Tunnelling Microscopy (STM). In this work we make a systematic study of the low temperature superconducting current densities J_s for different, Y:123 thin films. The magnetic field dependencies of the superconducting currents J_s are deduced from the hysteresis loops measured by torque magnetometry at T = 10 K. A comparative study of the magnetic properties with the micro-structure reveals that the island boundaries are strong candidates for being the pinning centres responsible for the large critical currents observed in our Laser Ablated and Sputtered thin films.