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

Abstract

We report local-magnetic-field measurements near a ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{y}}$ crystal by a linear array of Hall probes. Two distinct features are observed in the local-field hysteresis ${\mathit{H}}_{\mathit{l}}$ vs H, which are not present in the integrated magnetization measured by a SQUID: (1) a peak in ${\mathit{H}}_{\mathit{l}}$ 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 ${\mathit{H}}_{\mathit{l}}$ near zero external field which may be linked to ${\mathit{H}}_{\mathit{c}1}$. These local measurements suggest a relevant scale for the critical current variation of between 10 and 200 μm.