Magnetic field and current distributions at an artificial grainboundary in YBa2Cu3O7-x

Abstract

Using a magneto-optical technique, magnetic field distributions havebeen measured in melt-textured YBa2Cu3O7-x, joined toform an artificial grain boundary, in an external magnetic field perpendicularto the sample surface. An inversion scheme using the inverse-matrix method hasbeen applied to obtain the current distribution from the magnetic fielddistribution. Both magnetic field and current distributions around the grainboundary show different behaviour between the field increasing up to 150 mTand decreasing down to 0 T after zero-field cooling. The magnetic field at aweakly coupled section of the grain boundary in the increasing field is higherthan that in the decreasing field, even in the same external field. This studysupports a model in which such differences in the magnetic field at the weak-linkgrain boundaries give rise to the hysteresis behaviour in the field dependenceof transport critical current density in polycrystalline samples.