Magnetic flux penetration and distribution in Bi2Sr2CaCu2O single crystalsby magnetooptical measurements

Magnetic flux penetration and flux density distributions in Bi(2)Sr(2)CaCu( 2)Oy single crystals have been investigated by the magneto-optical techniqu e. In as-grown crystals, preferential flux penetration along narrow bands i n the a-direction is observed, independent of the geometry of the crystals. On annealing in flowing oxygen, flux penetration becomes more uniform but significantly anisotropic. Comparison with ac susceptibility measurements n ear T-c, suggests that inhomogeneous flux penetration in the as-grown cryst als may be associated with inhomogeneous oxygen stoichiometry.