Floating-zone growth and characterization of high-quality Bi2Sr2−xLaxCuO6+δ single crystals

Abstract High-quality Bi 2 Sr 2− x La x CuO 6+ δ (0⩽ x ⩽0.64) (La-doped Bi-2201) single crystals sized up to ∼20×5×1.0 mm 3 were successfully grown using the travelling-solvent floating-zone method. The effect of La substitution of Sr on the crystal growth, structure and superconducting properties was studied. Both X-ray diffraction (XRD) and neutron scattering measurements demonstrate the high quality of these crystals with mosaicity less than 0.5°. Powder XRD analysis indicates that the crystals possess the orthorhombic structure. The La-free Bi-2201 crystals do not show superconductivity down to 2 K, while the La-doped crystals exhibit superconductivity with transition temperature T c =20,28,33,15 and 12 K for samples with actual La content x =0.28,0.36,0.43,0.57 and 0.64, respectively. Upon decreasing carrier concentration (increasing La content x ), the in-plane resistivity ρ ab shows a change from metallic behaviour to a semiconductor-like behaviour in the low temperature region.