Friday, 2D-10, 4:40-4:50

A Reconsideration of Edge-Barrier Pinning in YBa₂Cu₃O_7-δ Thin Films

P. N. Barnes

J. A. Connors, R. L. Dunning, M. J. Mullins, T. J. Haugan

Propulsion Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 USA
Phone: (937) 255-4410, Fax: (937) 255-4307, E-mail: paul.barnes@wpafb.af.mil

J. R. Clem

Ames Laboratory, Iowa State University, Ames, Iowa 50011 USA

As improved pinning processes in thin films are made at various institutions, data are provided which are inevitably compared with each other. Most researchers account for the sample-thickness dependence when comparing the critical current density (J_c) values reported from various institutions. Tahara et al. have previously indicated that in narrow bridges, edge-barrier effects might be increasing the measured J_c in sample films as the bridges became increasing smaller [1]. Zhao et al. subsequently claimed that the edge-barrier pinning did not play a role in bridges down to a micron width based on experimental results, even though their data also reflected increasing J_c as bridges were decreased from 10 to 2 μm [2]. However, we provide theoretical calculations that suggest the edge-barrier pinning does play a substantial role in increasing Jc in YBa₂Cu₃O_7-δ (YBCO) thin films. Experimental data will be presented in addition to the theoretical study for clarification of this issue. In this case, bridges were narrowed on the same sample to avoid sample to sample variation in the films. YBCO films ~300 µm thick were deposited by pulsed laser deposition on lanthanum aluminate substrates. A 500 μm wide bridge was patterned on the sample using a photolithography process. After determining the critical current and resistivity of the films, the photolithography process was then repeated to further narrow the bridge to 200 μm, 100 μm and finally 50μm. The data by Zhao et al. will also be discussed in light of the new data. The enhancement of J_c can vary as a function of the applied field implying possible minor skewing of Jc(B) curves for a very narrow bridge.

[1] S. Tahara, S.M. Anlage, J. Halbritter, C.-B. Eom, D.K. Fork, T.H. Geballe, and M.R. Beasley, Phys. Rev. B 41, 11203 (1989).

[2] Y.J. Zhao, W.K. Chu, D.K. Christen, E.C. Jones, M.F. Davis, J.C. Wolfe, S.C. Deshmukh, and D.J. Economou, Appl. Phys. Lett. 59, 1129 (1991).

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