Influence of Fe buffer thickness on the crystalline quality and the transport properties of Fe/Ba(Fe1−xCox)2As2 bilayers

The implementation of an Fe buffer layer is a promising way to obtain epitaxial growth of Co-doped BaFe2As2 (Ba-122). However, the crystalline quality and the superconducting properties of Co-doped Ba-122 are influenced by the Fe buffer layer thickness, dFe. The well-textured growth of the Fe/Ba-122 bilayer with dFe=15 nm results in a high Jc of 0.45 MA cm−2 at 12 K in self-field, whereas a low Jc value of 61 000 A cm−2 is recorded for the bilayer with dFe=4 nm at the corresponding reduced temperature due to the presence of grain boundaries.