Effects of granularity and strong pinning on high frequency vortex dynamics in (Bi–Pb)2Sr2Ca2Cu3O10 superconducting platelets

An anomalous hysteretic behaviour is seen in the radio frequency penetration depth of unirradiated and heavy ion irradiated (Bi–Pb)2Sr2Ca2Cu3O10 platelets. Characterized by a large remanence, this anomaly is due to the high mobility of the magnetic flux trapped at the ubiquitous grain boundaries in these otherwise highly c-axis oriented samples. The range of temperature over which the hysteresis is seen depends on the strength of intragranular pinning. The observed behaviour is discussed quantitatively on the basis of the two-level critical state model of Ji, Rzchowski, Anand and Tinkham for microwave field penetration in inhomogeneous superconductors.