Nonstoichiometry of LixCu2O2+delta single crystal and its relation to magnetic ordering

We report the first systematic study on the nonstoichiometry of Li/Cu ionic ratios x and oxygen defect concentrations delta in LixCu2O2+delta solid solution. Nonstoichiometric crystals with intentional Li-deficient (x=0.97) or Li-excessive (x=1.06) concentrations were prepared by slow-cooling and floating-zone methods. By applying different oxygen pressures during growth, different magnitudes of oxygen defects were obtained, revealing varied magnetic and electrical properties. Our results strongly suggest that Li/Cu and oxygen nonstoichiometry in these crystals are responsible for the varied temperatures of helimagnetic ordering. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483244]