Li non-stoichiometry and crystal growth of untwinned 1D quantum spin system Lix Cu2 O2

TL;DR

This study reports the successful floating-zone growth of high-Li-content untwinned Li_xCu_2O_2 single crystals, accurately determining Li content and analyzing their morphology and magnetic properties, notably achieving a low helimagnetic ordering temperature.

Contribution

It demonstrates a method to grow high-quality untwinned Li_xCu_2O_2 crystals with high Li content using floating-zone technique and clarifies Li distribution without disorder.

Findings

Floating-zone growth yields large untwinned crystals with x ~ 0.99.

Li content determined accurately, ruling out disorder.

Lowest helimagnetic transition temperature ~19K achieved.

Abstract

Floating-zone growth of untwinned single crystal of Li_xCu_2O_2 with high Li content of x ~ 0.99 is reported. Li content of Li_xCu_2O_2 has been determined accurately through combined iodometric titration and thermogravimetric methods, which also ruled out the speculation of chemical disorder between Li and Cu ions. The morphology and physical properties of single crystals obtained from slowing-cooling (SL) and floating-zone (FZ) methods are compared. The floating-zone growth under Ar/O_2=7:1 gas mixture at 0.64 MPa produces large area of untwinned crystal with highest Li content, which has the lowest helimagnetic ordering temperature ~19K in the Li_xCu_2O_2 system.