Study of pinning effects for vortices in Bi2Sr2CaCu2O8+delta single crystals using a bitter decoration technique

Distribution of vortices has been analyzed to study on the pinning effects of the vortices in Bi2Sr2CaCu2O8+delta single crystals, observed with a Bit ter decoration technique. On the cleaved surfaces of the samples, vortices are pinned in the disordered configurations at lower magnetic fields, which change to a hexagonal lattice structure with increasing a magnetic field. Furthermore, a dense concentration of vortices has been observed in the voi ds and on the lower terrace of the steps. These distributions of the vortic es are found to be very stable from the estimation of the pinning energy.