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(Color online) (a) Sketch of a MOD coated conductor, in which laser cuts through the film define a bridge that channels the applied current. (b) Magnetic field over a section of the bridge, imaged via scanning Hall probe microscopy. Current forces flux into the film’s meandering grain boundaries. (c) Flux remains trapped when the current returns to zero. (d) Reconstructed current streamlines overlaid on show that the current spreads out along the boundaries, and its direction varies to accommodate their meandering. flows between neighboring streamlines.
[(a)–(f)] Magnetic images and reconstructed streamlines of current for each of three samples with grain boundaries tilted, as shown in (h), (j), and (m). The boundary between data and background calculation is identified in the (a) frames by a dashed green box. The magnetic images are all on the same color scale, shown in (a). See Ref. 9 for the full set of images presented as a movie. (g), (i), and (k) each plot one cycle with the applied currents and measured voltages for frames (a)–(f).
Critical current densities of tilted grain boundaries (GBs). The last row compares the intragrain . The “CR” column compares current density perpendicular to the GBs as reconstructed from magnetic images at .
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