Artificially induced reduction of the dissipation anisotropy in high-temperature superconductors

Abstract

Bi_2Sr_2CaCu_2O_8, RBa_2Cu_3O_7 (R=Y, Eu) thin films and RBa_2Cu_3O_7/PrBa_2Cu_3O_7 superlattices have been fabricated by sputtering technique. The anisotropic dissipation was measured close to the critical temperatures with high applied magnetic fields rotating from parallel to perpendicular to the substrate. In multilayers, in a large magnetic field interval, the dissipation anisotropy is reduced as much as 60% in comparison with the most anisotropic system (Bi_2Sr_2CaCu_2O_8) and at least 50% at 30 kOe in comparison with 123 films. This strong anisotropy reduction is discussed taking into account the role played by the superlattice modulation lengths on magnetic matching effects and coupling between the superconducting layers.