Spatially resolved magnetic hysteresis in a YBa2Cu3O7-y crystal measured by a Hall-probe array

We report local-magnetic-field measurements near a YBa2Cu3O7-y crystal by a linear array of Hall probes. Two distinct features are observed in the local-field hysteresis Hl vs H, which are not present in the integrated magnetization measured by a SQUID: (1) a peak in Hl right after the field reversal that we attribute to the field generated by the current flow in a platelike superconductor, and (2) a position-dependent suppression of Hl near zero external field which may be linked to Hc1. These local measurements suggest a relevant scale for the critical current variation of between 10 and 200 m. © 1992 The American Physical Society.