Growth and Accurate Characterization of Bi2Sr2−xLaxCuO6+δ Single Crystals

High-quality and various doped Bi 2 Sr 2− x La x CuO 6+ δ ( x =0–0.90) single crystals were obtained by floating-zone method. Analysis of the thermal behavior indicated an incongruent melt for all the doped compounds. The segregation coefficient of La related to Sr was estimated to be ∼1.02. Chemical compositions including the La doping in the crystals were accurately determined to study the effect of doping on the structural, chemical and superconducting property of the compounds. Raman spectra were performed to show the high-frequency modes 627 cm −1 softened with increasing the doping level of La. Implications of the doping effect on crystals for understanding the superconductivity are discussed.