INDUCTIVE CRITICAL CURRENTS IN LN2-XCEXCUO4 SINGLE-CRYSTALS - THE EFFECT OF THERMAL-ACTIVATION

Hysteresis-cycles and remanent-magnetization data are used to obtain t he temperature and field dependences of the irreversible magnetization , M(irr)(T, H). We show that the critical currents, evaluated under th e assumption of a critical-state model, display an exponential decay w ith field; the field and temperature dependences cannot be factorized. We argue that the latter feature, together with the strong temperatur e dependence of M(irr)(T, H), might be due to magnetic relaxation. The effect of thermally activated flux motion on the measured M(irr)(T, H ) is analyzed to get an insight into the actual temperature and field dependences of J(c)(T, H).