Influence of substrate type on transport properties of superconducting FeSe0.5Te0.5 thin films

TL;DR

This study investigates how different substrates influence the structural and superconducting transport properties of FeSe0.5Te0.5 thin films, revealing substrate-dependent crystalline quality and defect structures affecting critical current behavior.

Contribution

It provides new insights into the substrate effects on the crystalline quality and superconducting properties of FeSe0.5Te0.5 thin films, highlighting the role of c-axis defects and anisotropic scaling.

Findings

MgO induces c-axis defects affecting Jc({ heta}) peaks.

Jc({ heta}) scales with anisotropic Ginzburg-Landau approach.

Anisotropy ratio {b3}J decreases with temperature.

Abstract

FeSe0.5Te0.5 thin films were grown by pulsed laser deposition on CaF2, LaAlO3 and MgO substrates and structurally and electro-magnetically characterized in order to study the influence of the substrate on their transport properties. The in-plane lattice mismatch between FeSe0.5Te0.5 bulk and the substrates shows no influence on the lattice parameters of the films, whereas the type of substrates affects the crystalline quality of the films and, therefore, the superconducting properties. The film on MgO showed an extra peak in the angular dependence of critical current density Jc({\theta}) at {\theta} = 180{\deg} (H || c), which arises from c-axis defects as confirmed by transmission electron microscopy. In contrast, no Jc({\theta}) peaks for H || c were observed in films on CaF2 and LaAlO3. Jc({\theta}) can be scaled successfully for both films without c-axis correlated defects by the anisotropic Ginzburg-Landau (AGL) approach with appropriate anisotropy ratio {\gamma}J. The scaling parameter {\gamma}J is decreasing with decreasing temperature, which is different from what we observed in FeSe0.5Te0.5 films on Fe-buffered MgO substrates.