CRITICAL-STATE INSTABILITIES OBSERVED ON YBCO-CERAMICS AT ULTRALOW FIELDS NEAR T-C

Comparing our experimental data collected on intermediate-states insta bilities in YBCO superconductors with similar data published in the li terature for type-II superconductors we suggest the following: the occ urrence of oscillations and limited flux jumps (initiated by external perturbations) in ceramic YBCO superconductors are in no obvious way d ifferent from that initiated by magnetic field perturbations in type-I I superconductors. For this reason the validity of the adiabatic-stabi lity conditions of the critical state determined for type-II supercond uctors could be extended to the instabilities in Y based superconducto rs. Copyright (C) 1996 Elsevier Science Ltd