Li nonstoichiometry and crystal growth of an untwinned one-dimensional quantum spin system Li_xCu₂O₂

Floating-zone growth of untwinned single crystal of Li_xCu ₂O₂ with high Li content of x∼0.99±0.03 is reported. Li content of Li_xCu₂O₂ has been determined accurately through combined iodometric titration and thermogravimetric (TGA) 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 and floating-zone methods are compared. The floating-zone growth under Ar/O₂=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 ∼19 K in the Li _xCu₂O₂ system.