MAGNETIC HYSTERESIS AND MAGNETIC-RELAXATION STUDIES IN BI-V-SR-CA-CU-O SUPERCONDUCTING SYSTEM

We report magnetic hysteresis and magnetic relaxation studies on Bi2-x VxSr2Ca2Cu3Oy superconducting system. We have determined the temperatu re and field dependent critical current density J(c) and pinning force density F-pin from magnetic hysteresis studies and the activation ene rgy U-0 from magnetic relaxation measurements of the sample Bi1.6V0.4S r2Ca2Cu3Oy Temperature dependent J(c) and activation energy U-0 studie s suggested that at low temperatures pinning centres and low activatio n energy are active and in high temperatures pinning centres with high activation energy are dominating. The field dependent J(c) and F-pin measurements showed that pinning is mainly due to twin boundaries at l ow temperature (< 20 K). In addition, we have also determined the temp erature dependent lower critical field. Possible reasons for variation of lower critical field with temperature were discussed.