Flux pinning in YBa2Cu3O7-δ thin films with ordered arrays of columnar defects

Ordered arrays of columnar defects have been fabricated by direct electron-beam writing on c_⊥-oriented YBa₂Cu₃O_7-δ (YBCO) thin films. Serving as strong pinning sites, columnar defects cause a 70% enhancement of critical current density J_c at T=77 K in magnetic 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 this way of pinning center fabrication could be a promising tool in studies of the pinning mechanism in high-temperature superconductors.