SIMULTANEOUS OBSERVATION OF COLUMNAR DEFECTS AND MAGNETIC-FLUX LINES IN HIGH-TEMPERATURE BI2SR2CACU2O8 SUPERCONDUCTORS

Columnar defects generated by heavy-ion irradiation are promising stru ctures for pinning magnetic flux lines and enhancing critical currents in superconductors with high transition temperatures. An approach tha t combines chemical etching and magnetic decoration was used to highli ght simultaneously the distributions of columnar defects and magnetic flux lines in Bi2Sr2CaCu2O8 superconductors. Analyses of images of the columnar defects and flux-line positions provide insight into flux-li ne pinning by elucidating (i) the occupancy of columnar defects by flu x lines, (ii) the nature of topological defects in the flux-line latti ce, and (iii) the translational and orientational order in this lattic e.