Effects of Iodine Annealing on Fe1+yTe0.6Se0.4

TL;DR

This study systematically investigates how iodine annealing enhances bulk superconductivity in Fe1+yTe0.6Se0.4, identifying optimal conditions and suggesting iodine acts as a catalyst by consuming excess iron to form FeTe2.

Contribution

It reveals the optimal iodine annealing conditions for inducing bulk superconductivity and proposes a catalytic role of iodine in removing excess iron.

Findings

Optimal iodine ratio of 5-7% at 400°C induces superconductivity.

Superconducting transition temperature (Tc) ~14.5 K and critical current density ~5x10^5 A/cm2.

Excess iron is consumed to form FeTe2, with no iodine-containing compounds detected.

Abstract

Effects of iodine annealing to induce bulk superconductivity in Fe1+yTe0.6Se0.4 have been systematically studied by changing the molar ratio of iodine to the sample and annealing temperature. The optimal condition to induce bulk superconductivity with Tc ~14.5 K and self-field Jc(2 K) ~ 5x10^5 A/cm2 is found to be a molar ratio of iodine of 5-7 % at the annealing temperature of 400 C. Furthermore, the fact that no compounds containing iodine are detected in the crystal and a significant amount of FeTe2 is produced after the iodine annealing strongly indicate that the excess iron is consumed to form FeTe2 and iodine works as a catalyst in this process.