Using a vibrating-reed technique, we studied the flux penetration in YBa2Cu3O7- single crystals in the strong pinning regime well below the irreversibility line. The resonant frequency and damping of the vibrating superconductor are dramatically enhanced by the nonuniform and hysteretical penetration of the flux lines at low temperature. Using a critical-state model, we determine the critical current density Jc to be about 3.5×106 A/cm2 at 4.2 K. We also found that Jc obeys an exponential temperature dependence and the flux creep at low temperature can be characterized by a low activation energy barrier on the order of 20 K.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics