Size effects in the magnetisation of high T/sub c/ powders

The critical-current and flux profile within a series of different size powders of YBa/sub 2/Cu/sub 3/O/sub 7/ has been measured. At zero field, supercurrents flow unimpeded within the grains. However, for fields above 100 mT, it appears that the grains are subdivided on a scale smaller than 1 mu m. Using this interpretation it is found that the interaction of the fluxoids with the pinning centers is very similar to that taking place in V/sub 3/Si and commercial NbTi.<
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