Comparison of Superconducting Properties of <formula formulatype='inline'><tex Notation='TeX'>$ \hbox{FeSe}_{0.5}\hbox{Te}_{0.5}$</tex></formula> Thin Films Grown on Different Substrates

We have shown that the superconducting properties of FeSe0.5 Te0.5 thin films are strongly dependent on the growth conditions and, in particular, the in-plane lattice constant of the substrate influences the crystallographic lattice parameters of the films, affecting the strain and is responsible for strong enhancements of the critical temperature Tc and for the introduction of different pinning mechanisms. Here we compare the structural, electrical and transport properties of superconducting Fe(Se0.5, Te0.5) epitaxial films deposited through pulsed laser ablation on three different substrates namely lanthanum aluminate (LaAlO3), strontium titanate (SrTiO3), and calcium fluoride (CaF2). We analyze in particular the critical current density Jc as a function of the temperature and magnetic field, and its anisotropy, which is related to the different pinning mechanisms in play. The film grown on SrTiO3 exhibits a higher critical current when the field is perpendicular to the film surface, opposite to what happens in the sample grown on LaAlO3 due to the presence of extrinsic pinning along the c-axis, while we observe almost no anisotropy on the thin film grown on CaF2.