Size Dependence of Oxygen-annealing Effects on Superconductivity of Fe{1+y}Te{1-x}S{x}

TL;DR

This study explores how the size of Fe{1+y}Te{1-x}S{x} samples influences the effectiveness of oxygen annealing in inducing bulk superconductivity, revealing an optimal size for maximum superconducting volume.

Contribution

It demonstrates the size dependence of oxygen annealing effects on superconductivity in Fe-based superconductors, highlighting a surface-limited mechanism.

Findings

Superconductivity is optimized at a specific sample size.

Oxygen annealing affects only a surface layer of a few tens of micrometers.

Bulk superconductivity depends on sample size and surface effects.

Abstract

For the Fe-based superconductor Fe{1+y}Te{1-x}S{x}, superconductivity is induced by annealing treatment in oxygen atmosphere, whereas as-grown samples do not show superconductivity. We have investigated the sample-size dependence of O2-annealing effects in Fe1.01Te0.91S0.09. The annealing conditions are fixed to be 1 atm, 200 C, and 2 hours. We have carried out magnetic susceptibility and specific heat measurements in order to evaluate the superconducting volume fraction. We have found that Fe{1+y}Te{1-x}S{x} has an optimal size for the induction of bulk superconductivity by O2 annealing. Our results indicate that O2 annealing is probably effective near the surface of samples over a length of a few tens of micro meters.