VORTEX PHASE-DIAGRAM OF BI2SR2CACU2O8- C-AXIS SUPERCONDUCTING CORRELATION IN THE DIFFERENT VORTEX PHASES(DELTA )

The vortex phase diagram in Bi2Sr2CaCu2O8+delta is investigated by stu dying the linear ac transverse permeability mu(perpendicular to) = mu( perpendicular to) + mu(perpendicular to)'' (h(ac)perpendicular to H pa rallel to c axis) in a wide range of temperature and magnetic fields. At low fields (H<300 Oe) superconducting phase coherence in the c dire ction shows that the ordered vortex solid state is characterized by a c-axis vortex correlation length l(c) limited by the sample thickness d. At low temperatures (T<20 K) point disorder is sufficiently strong and the phase coherent ordered vortex solid becomes metastable. In the temperature range 20<T<42 K when the applied field exceeds H-ent(T), the ordered vortex state transforms into an entangled state with no in dication of reduction of l(c). At a higher crossover field the linear response becomes Ohmic, l(c)<d. At higher temperatures the vortex stru cture becomes an uncorrelated vortex liquid in all directions. [S0163- 1829(98)02706-4].