Critical Currents of Superconducting Y-Ba-Cu, Dy-Ba-Cu and Gd-Ba-Cu Oxides in Low Magnetic Fields

Critical currents I c of Y-Ba-Cu-O, Dy-Ba-Cu-O and Gd-Ba-Cu-O systems have been measured in a low magnetic field H above 77 K. For increase and decrease of H, I c(H) shows hysteresis similar to that in superconducting bridges. The hysteresis in oxide samples is explained by taking into account the inclusion of such superconducting, narrow parts as in bridges.