Distribution of magnetic flux in high-Tc grain-boundary junctions enclosing hexagonal and triangular areas

We report here scanning superconducting quantum interference device microscope measurements of the magnetic-flux-threading grain-boundary junctions that completely enclose hexagonal and triangular regions. While the total flux through one of these junctions is nΦ0, there are distinct areas of localized flux with magnitudes much less than Φ0. We present the experimental results and discuss possible explanations for these observations. © 1995 The American Physical Society.