STRUCTURES AND EFFECTS OF RADIATION-DAMAGE IN CUPRATE SUPERCONDUCTORSIRRADIATED WITH SEVERAL-HUNDRED-MEV HEAVY-IONS

This paper reports a study of the nature and systematic variation of r adiation damage to cuprate superconductors caused by several-hundred-M eV heavy ions. While irradiation Of YBa2Cu3O7-delta with 300-MeV Au24 and 276-MeV Ag21+ ions produces columns of amorphous material along t he ion trajectories, such defects are only created occasionally during irradiation with 236-MeV Cu18+ and not induced with 182-MeV Si13+. A comparative study of the defect formation in Bi2Sr2Ca2Cu3Ox and oxygen -reduced and ozone-treated YBa2Cu3O7-delta, shows that the degree of t he radiation damage by the heavy ions depends on (a) the rate at which ions lose their energy in the target; (b) the crystallographic orient ations with respect to the incident ion beam; (c) thermal conductivity and chemical state (oxygen concentration for YBa2Cu3O7-delta) of the sample; and (d) the extent of preexisting defects in the crystal. A th eoretical model based on ion-induced localized melting and the effects of anisotropic thermal conductivity of these materials provides a bas is for understanding the size and shape of the amorphous tracks. Measu rements of the superconducting properties of Au24+- and Ag21+-irradiat ed YBa2Cu3O7-delta thin films show a universal linear scaling between the fractional areal damage versus the superconducting transition temp erature and the normal-state resistivity.