Magnetic field and current distributions in melt-textured YBa2 Cu3O7-x with an artificial grain boundary

Using a magneto-optical (MO) technique, magnetic field distributions have been measured in a melt-textured YBa₂Cu ₃O_7-x bulk superconductor, joined to form an artificial grain boundary (GB), in an external magnetic field perpendicular to the sample surface. The magnetic field at a weak section of the GB shows different values between the field increasing up to 150 mT and decreasing down to 0 T after zero-field-cooling. Namely, the magnetic field in increasing field is higher than that in decreasing field, even in the same external field. This result supports a model in which such differences in magnetic field at the weak-link GB give rise to the hysteresis behavior in the field dependence of transport critical current density in polycrystalline samples. The field distributions across a well-joined region of the GB behave similarly to the adjoining bulk material and this result indicates the possibility of creating useful artifacts provided that the strongly coupled sections can be reproduced on a larger scale