Thickness dependence of critical current density in RABiTS coated conductors.

The critical current density $J_c$ flowing in thin $YBa_2Cu_3O_{7-\delta}$ (YBCO) films of various thicknesses $d$ has been studied magnetometrically, both as a function of applied field $H$ and temperature $T$. The films, grown by a BaF2 ex-situ process and deposited on buffered `RABiTS' substrates of Ni-5W, have thicknesses ranging from 28 nm to 1.5 $\mu$m. The $J_c$ increases with thickness at first, peaks at about d $\sim$ 120 nm, and decreases with thickness thereafter. In intermediate applied magnetic fields, we find a power law falloff $J_c \propto H^{-\beta}$ with $\beta$ $\sim$ (0.56 - 0.69) for all the samples. Temperature dependence of the $J_c$ is also studied.