Flux penetration profiles in powdered DyBa2Cu3O7

Flux penetration measurements on powdered specimens of DyBa2Cu3O7 have been performed by using Campbell's [J. Phys., C 2, 1492 (1969)] method at 4.2 K in magnetic fields up to 7 T. There are three principal results of the measurements. The first is that although there is a small region of surface current, there is indeed a linear bulk flux profile. Thus there is a uniform bulk current flowing through the sample, and the Bean model is appropriate for these compounds. The second result is that the magnetic moment is independent of particle size (over the range 3--12 μm), even when the powders are single crystals. This implies that the currents are subdivided on a scale finer than the grain size. The third result is that J/sub c/ (4.2 K, 1--7 T) is very high, reaching 107 A/cm2