High-pressure self-flux growth and characterization of Li-deficient Li0.95FeAs single crystals

TL;DR

This study reports the high-pressure self-flux growth of nearly stoichiometric Li0.95FeAs single crystals, characterizing their structure and superconducting properties, and analyzing the effects of Li deficiency on superconductivity.

Contribution

It introduces a high-pressure method for growing high-quality Li-deficient LiFeAs crystals and provides detailed structural and superconducting property analysis.

Findings

Crystals exhibit bulk superconductivity at 16 K.

Li deficiency has minimal impact on superconductivity.

Superconductivity is suppressed by Fe excess and Li deficiency.

Abstract

Single crystals of LiFeAs were successfully grown by a self-flux method using the cubic anvil high-pressure and high-temperature technique. The reaction took place in a closed boron nitride crucible at a pressure of 1 GPa and a temperature of 1050 C. The grown crystals, retrieved from solidified lump, exhibit plate-like shapes with sizes up to 0.7 x 0.7 x 0.15 mm3. Single-crystal x-ray diffraction refinement confirmed the high structural perfection of the grown crystals (space group P4/nmm, No 129, Z = 2, a = 3.77370(10) A, c = 6.3468(6) A, and V = 90.384(9) A3) with the presence of a small deficiency on the Li site. The refined chemical composition of the produced crystals is Li0.95FeAs. Temperature-dependent magnetization measurements revealed bulk superconductivity with a superconducting transition Tc = 16 K. A comparative analysis of LiFeAs, Li1-xFeAs, and Li1-yFe1+yAs systems reveal that superconductivity is less sensitive to the Li deficiency, although it may completely disappear in the presence of both Fe excess and Li deficiency.