Suppression of vortex pinning by field component parallel to the superconducting plane in Bi2Sr2CaCu2O8

The response of magnetic fluxoids nearly parallel to the superconducting pl ane of the layered superconductor Bi2Sr2CaCu2O8 has been investigated throu gh the ac susceptibility measurement. The fluxoids respond diamagnetically due to pinning when they pierce the superconducting plane to form pancake v ortices, but they are released due to melting and become mobile in the high field. The liberation is enhanced by approaching the parallel field direct ion by the effect of decoupling between planes and finally the vortex pinni ng is suppressed. The pinning of fluxoids with pancakes and releasing in re lation to their lock-in state are presented.