CRITICAL DYNAMIC FIELD IN YBACUO AND BISRCACUO COMPOUNDS - A COMPARATIVE-STUDY OF SOME HIGH-TEMPERATURE SUPERCONDUCTORS BY LOW FIELD COMPLEX SUSCEPTIBILITY

A comparative study of the low field susceptibility of 123 high temperature superconducting compounds and Bi compounds is presented. Results are discussed using the dynamic critical field model of Mehdaoui et al. (1989,1990). The low critical dynamic fields and the corresponding low pinning energies obtained in the case of Bi compounds (when compared with 123 compounds) are consistent with other data about activation energy and explain the dependence of electrical resistivity upon measuring currents. The high temperature phase (T c=110 K) also has much higher pinning than the low temperature phase (Tc=80 K) in the Bi compounds.