Vortex dynamics in Bi2Sr2CaCu2O8+delta single crystals with planar defects

We have studied the effects of c-axis correlated planar defects on the vort ex lattice of Bi2Sr2CaCu2O8 single crystals using Bitter decoration, transv erse ac permeability and X-ray measurements. Our results show that the low field low temperature phase coherent vortex lattice exhibits anisotropic pi nning in the presence of these planar defects. Frequency dependent ac perme ability measurements show that the ordered solid-liquid transition is first order as in samples free of correlated defects. However, the melting point is detected only when the excitation field is along the defects. (C) 2001 Elsevier Science Ltd. All rights reserved.