OXYGEN-DEFECT FLUX PINNING, ANOMALOUS MAGNETIZATION AND INTRAGRAIN GRANULARITY IN YBA2CU3O7-DELTA

The anomalous magnetization characteristic, intra-grain granularity and the magnitude of the flux pinning in single crystals of YBa2Cu307-δ are shown to be intimately linked. As the nominal oxygen deficiency δ decreases towards zero, the flux pinning declines and the crystals lose their explicitly granular signature. As δ is seldom specifically controlled at levels below ∼0.05 in even the most carefully made materials, small oxygen deficiencies may contribute significantly to both the flux pinning and the weak-link properties. © 1990 Nature Publishing Group.