Influence of Fe buffer thickness on the crystalline quality and the transport properties of Fe/Ba(FeCo)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, d_Fe. The well-textured growth of the Fe/Ba-122 bilayer with d_Fe = 15 nm results in a high J_c of 0.45 MA cm⁻² at 12 K in self-field, whereas a low J_c value of 61 000 A cm⁻² is recorded for the bilayer with d_Fe = 4 nm at the corresponding reduced temperature due to the presence of grain boundaries.