Artificial and self-assembled vortex-pinning centers in superconducting Ba(Fe_(1-xCox)_2As_2 thin films as a route to obtaining very high critical-current densities

摘要

We report on the superior vortex pinning of single- and multilayer Ba(Fe_(1-xCox)_2As_2 thin films with self-assembled c-axis and artificially introduced ab-plane pins. Ba(Fe_(1-xCox)_2As_2 can accept a very high density of pins (15-20 vol %) without T_c suppression. The matching field is greater than 12 T, producing a significant enhancement of the critical current density J_c, an almost isotropic J_c(θ, 20 T) > 10~3 A/cm~2, and global pinning force density F_p of -50 GN/m~3. This scenario strongly differs from the high-temperature superconducting cuprates where the addition of pins without T_c suppression is limited to 2-4 vol %, leading to small H_(Irr) enhancements and improved J_c only below 3-5 T.