FLUX-PINNING IN YBA2CU3O7-DELTA THIN-FILMS WITH ORDERED ARRAYS OF COLUMNAR DEFECTS

Ordered arrays of columnar defects have been fabricated by direct elec tron-beam writing on c(perpendicular to)-oriented YBa2Cu3O7-delta (YBC O) thin films. Serving as strong pinning sites, columnar defects cause a 70% enhancement of critical current density J(c) at T=77 K in magne tic fields parallel to the c axis. The matching effect of the pinning force density has been observed, due to commensurability between flux lines and arrays of columnar defects. The pinning strength of columnar defects has been compared with that of point defects, and found to be greater than the latter in YBCO films. These results suggest that thi s way of pinning center fabrication could be a promising tool in studi es of the pinning mechanism in high-temperature superconductors.