FLUX-FRONT MOTION PARALLEL TO CUO2 PLANES IN YBA2CU3O7-DELTA OBSERVEDWITH A SCANNING HALL PROBE

The motion of the flux front in YBa2Cu3O7-delta With the field applied parallel to the layers is studied using a scanning Hall probe. By tra cking the peak positions versus field in the remanence, we determine d irectly the critical current density perpendicular to the layers (J(c) is-perpendicular-to = 8.3 X 10(4) A/cm2 at 4.2 K). The observed critic al-current anisotropy (approximately 500) is much larger than indicate d by high-temperature measurements. By scanning the flux profiles in t he direction perpendicular to the layers, we find direct evidence that flux motion occurs parallel to the layers. A model that accounts for the observed mountain-pass topography in the remanence is presented.