MAGNETIC MEASUREMENTS ON TL-2212 AND BI-2212 SINGLE-CRYSTALS - A COMPARATIVE-STUDY

We have compared the magnetic behaviour of two identicaly shaped single crystals, Tl2Ba2CaCu2O8 and Bi2Sr2CaCu2O8. The critical current density is found to decrease more rapidly with temperature in Bi-2212 although it is the highest in this material at low temperatures (T < 20K). I-V characteristic curves have been obtained from measurements of magnetic sweep rate dependencies of the hysteresis loops. We have found that the characteristic temperature at which flux motion becomes important is significantly higher in Tl-2212 than in Bi-2212. Hence the Tl-2212 has a larger effective pinning