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

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.