STUDIES OF MAGNETIZATION CURRENTS IN YBA2CU3O7-X SUPERCONDUCTORS

The trapped magnetic field of melt-textured Y-Ba-Cu-O samples has been studied. The measured field distributions can be well reproduced by a simple two-current model consisting of a constant surface current and a constant volume current. If the sample is maximally magnetized (sat urated case), the remnant sample magnetic moment can be calculated fro m the two-current model, and the results agree with vibrating sample m agnetometer measurements to typically 10%. J(c) of the sample can then be obtained. The application of the two-current model to the analysis of the nonsaturated case is also reported, for both field-cooled and zero-field-cooled samples. The experimental data show the general feat ures predicted by the Bean model, which, however, has to be modified t o account for the data quantitatively.