Single Crystal Growth and Characterization of the Iron-Based Superconductor KFe2As2 Synthesized by KAs Flux Method

TL;DR

This paper reports the successful growth of large, high-quality single crystals of the iron-based superconductor KFe2As2 using a KAs flux method, and characterizes their superconducting properties.

Contribution

It introduces a self-flux growth technique with an encapsulation method to produce large, high-quality KFe2As2 single crystals for the first time.

Findings

Crystals up to 15 mm x 10 mm x 0.4 mm were grown.

Superconducting transition at 3.4 K with 0.2 K width.

Residual resistivity ratio exceeds 450.

Abstract

Centimeter sized platelet single crystals of KFe2As2 were grown using a self-flux method. An encapsulation technique using commercial stainless steel container allowed the stable crystal growth lasting for more than 2 weeks. Ternary K-Fe-As systems with various starting compositions were examined to determine the optimal growth conditions. Employment of KAs flux led to the growth of large single crystals with the typical size of as large as 15 mm x 10 mm x 0.4 mm. The grown crystals exhibit sharp superconducting transition at 3.4 K with the transition width 0.2 K, as well as the very large residual resistivity ratio exceeding 450, evidencing the good sample quality.