Crossover in magnetization behavior of Bi2212:Pb single crystal

Abstract Magnetic flux penetration in Bi 1.9 Pb 0.3 Sr 2 CaCu 2 O 8 single crystals in crossed fields is studied by magnetooptic technique. The anisotropy of the flux penetration induced by in-plane field is observed at temperatures below T m =54±2 K . The anisotropy increases with temperature if T T m . No correlation between the in-plane field and the out-of-plane flux penetration is observed for T > T m . This anisotropy is an evidence of a strong correlation between pancake vortices in different CuO planes. The vortex lattice behaves like 3D system at T T m and like 2D one at T > T m .