Vortex phases in magnetic fields near ab-plane in Bi2Sr2CaCu2O8+delta single crystal

Vortex matter of the layered superconductors in very high magnetic fields near the ab-plane was studied by using the c-axis resistivity measurements on the mesoscopic Bi2Sr2CaCu2O8+delta single crystals. While the angular dependence of resistance exhibits the sharp lock-in features in low magnetic field region, it was found that the vortex lock-in transition becomes considerably broad in high magnetic fields, showing anomalous shoulders at 0.3 degrees away from the ab-plane. The appearance of the resistance shoulder is followed with the stronger current level dependence, indicating possible different phases due to interplay of Josephson vortices and pancake vortices near ab-plane