Transport properties of the single- and 3-core Fe-Se wires fabricated by a novel chemical-transformation PIT process

TL;DR

This paper reports a novel chemical transformation process to fabricate Fe-Se superconducting wires with improved packing density, demonstrating superconductivity below 10 K and high upper critical fields, with detailed transport properties.

Contribution

Introduction of a chemical transformation PIT process to produce Fe-Se wires with enhanced superconducting properties and higher critical current densities.

Findings

Superconductivity observed below ~10 K.

Upper critical field estimated at 19.3 T.

Transport critical current densities of 588 A/cm2 (3-core) and 218 A/cm2 (single-core).

Abstract

We fabricated single- and 3-core superconducting Fe-Se wires using a novel process based on a chemical transformation from hexagonal FeSe1+d (non-superconducting) to tetragonal FeSe (superconducting) via an optimal supply of Fe from the Fe sheath by annealing. This process enhanced a packing density of superconducting core inside the sheath, owing to an expansion of the lattice volume via a chemical transformation from high-density hexagonal FeSe1+d to low-density tetragonal FeSe. The obtained superconducting wire showed superconductivity below ~10 K and the upper critical field was estimated to be 19.3 T at 0 K. The obtained transport critical current densities at 0 T were 588 A/cm2 for the 3-core wire and 218 A/cm2 for the single-core wire.