Current persistence and magnetic shielding properties of Y1Ba2Cu3Ox tubes.

We have studied the time and temperature dependence of trapped magnetic fields in ceramic tubes of the high-${T}_{c}$ superconductor ${\mathrm{Y}}_{1}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{x}$. The maximum field in a particular tube is largely a function of temperature, although decays of the form ${t}^{\ensuremath{-}\ensuremath{\alpha}}$ occur for fields at the maximum values. For fields away from the critical values, limits on the decay rates give $\ensuremath{\rho}\ensuremath{\le}{10}^{\ensuremath{-}16}$ \ensuremath{\Omega} cm. These results are consistent with the superconductor being in a spin-glass-like state.