The effect of Ag addition on the superconducting properties of the FeSe system

TL;DR

Adding silver to FeSe superconductors enhances their intergranular and intra-granular properties, increasing critical current, irreversibility field, and overall superconducting performance, as shown by magnetic susceptibility analyses.

Contribution

This study demonstrates that silver addition improves superconducting properties of FeSe0.94, specifically enhancing critical current and irreversibility fields, which was not previously established.

Findings

Intergranular critical current increased with Ag addition

Irreversibility field is higher in Ag-doped samples

Ag improves pinning and screening ability

Abstract

The tetragonal FeSe phase is an intensively investigated iron based superconductor. In this study we examined the influence of Ag addition on the superconducting properties of selenium deficient polycrystalline FeSe0.94. The samples were obtained by solid state reaction and melting methods. XRD analysis shows the presence of tetragonal phase and EDX analysis establishes inhomogeneous Ag distribution in the grains. The superconducting properties were investigated by fundamental and third harmonic AC magnetic susceptibility. The intergranular critical current determined from AC magnetic susceptibility in the Ag doped sample is several times higher than that in the undoped one, obtained by melting at approximately the same temperatures. Intra-granular current is field independent up to almost 1000 Oe. Using the temperature dependence of third harmonic AC magnetic susceptibility at different DC magnetic fields, the irreversibility lines were obtained for all samples. It is found that Ag addition increased the irreversibility field in comparison with undoped melted and powder sintered samples. All results show that the Ag addition in selenium deficient (FeSe0.94) samples leads to improvement of inter- and intra- granular properties: screening ability, pinning, activation energy and critical current and improves the irreversibility line.