MAGNETIC HYSTERESIS AND MAGNETIC RELAXATION STUDIES IN Bi-V-Sr-Ca-Cu-O SUPERCONDUCTING SYSTEM

Abstract

We report magnetic hysteresis and magnetic relaxation studies on Bi 2−x V x Sr 2 Ca 2 Cu 3 O y superconducting system. We have determined the temperature and field dependent critical current density J c and pinning force density F pin from magnetic hysteresis studies and the activation energy U0 from magnetic relaxation measurements of the sample Bi 1.6 V 0.4 Sr 2 Ca 2 Cu 3 O y. Temperature dependent J c and activation energy U0 studies suggested that at low temperatures pinning centres and low activation 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 low temperature (<20 K). In addition, we have also determined the temperature dependent lower critical field. Possible reasons for variation of lower critical field with temperature were discussed.