A study of the reversible and irreversible magnetic properties of a Bi-2212 single crystal in high magnetic fields

A study of the magnetic properties of Bi-2212 single crystals in dependence on field, temperature and time has been carried out in fields up to 14T and in the temperature range 1.8-150 K. The field dependence of the critical current and pinning force density scales with the irreversibility field B*(T) leading to B*(0)=120 T for H//c and ξ ab(0) ≅ 16.5 AA. From an analysis of the irreversibility line in the framework of the vortex glass theory the 2D melting temperature of the vortex lattice and the 3D-2D crossover field was determined: TM2D ≅ 29 K and B2D ≅ 1.1 T. The magnetic relaxation processes yield very low activation energies of U0 ≅ 15-20 meV for field directions perpendicular and parallel to the c axis. Deviations from simple logarithmic time decay were observed in the temperature range around 20 K. From an analysis of the reversible magnetization the penetration depth was estimated to be λ ab ≅ 1490 AA. The diamagnetism above the mean-field phase transition temperature can be described within the framework of a 2D fluctuation model. (author)