Imaging ac losses in superconducting films via scanning Hall probe microscopy

Rafael B. Dinner, Kathryn A. Moler, D. Matthew Feldmann, and M. R. Beasley
Phys. Rev. B 75, 144503 – Published 4 April 2007
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Abstract

Various local probes have been applied to understanding current flow through superconducting films, which are often surprisingly inhomogeneous. Here, we show that magnetic imaging allows quantitative reconstruction of both current density J and electric field E resolved in time and space in a film carrying subcritical ac current. Current reconstruction entails inversion of the Biot-Savart law, while electric fields are reconstructed using Faraday’s law. We describe the corresponding numerical procedures, largely adapting existing work to the case of a strip carrying ac current, but including other methods of obtaining the complete electric field from the inductive portion determined by Faraday’s law. We also delineate the physical requirements behind the mathematical transformations. We then apply the procedures to images of a strip of YBa2Cu3O7δ carrying an ac current at 400Hz. Our scanning Hall probe microscope produces a time series of magnetic images of the strip with 1μm spatial resolution and 25μs time resolution. Combining the reconstructed J and E, we obtain a complete characterization including local critical current density, EJ curves, and power losses. This analysis has a range of applications from fundamental studies of vortex dynamics to practical coated conductor development.

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  • Received 27 November 2006

DOI:https://doi.org/10.1103/PhysRevB.75.144503

©2007 American Physical Society

Authors & Affiliations

Rafael B. Dinner1, Kathryn A. Moler1,*, D. Matthew Feldmann2, and M. R. Beasley1

  • 1Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA
  • 2Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

  • *Electronic address: kmoler@stanford.edu

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Issue

Vol. 75, Iss. 14 — 1 April 2007

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