Modifications of pinning properties induced by introduction of columnar defects in a (Hg 0.8Cu 0.2)Ba 2CuO 4+ δ single crystal

Abstract

Columnar defects have been introduced along the c axis of a (Hg 0.8Cu 0.2)Ba 2CuO 4+ δ (Hg-1201) single crystal by irradiation with 6 GeV Pb ions. The nature of the induced latent tracks has been characterized by high-resolution electron microscopy (HREM). The resulting modifications of pinning properties have been inferred from magnetic measurements carried out, before and after irradiation, with the field applied along the c-axis. We have investigated the induced effects on the critical temperature, the field and temperature dependences of the persistent current density, and the irreversibility line. A detailed study of vortex dynamics in the presence of columnar defects has been carried out on the basis of relaxation experiments. It is demonstrated that, with correlated disorder, Hg-1201 exhibits features very similar to those previously reported in YBa 2Cu 3O 7 (YBCO), despite a much larger electronic anisotropy.