Crystal growth and superconducting properties of Bi{sub}2Sr{sub}2Ca{sub}2Cu{sub}3O{sub}y(Bi2223) single crystals

摘要

Bi2223 single crystals were grown by the floating zone method with an extremely slow growth rate of 0.05 mm/h. The largest size of the plate-like single crystal was approximately 3 × 2 × 0.1 mm{sup}3. The X-ray diffraction analysis and DC susceptibility measurements revealed that the grown crystals were almost single phase of Bi2223 with a very small percentage of Bi2212 intergrowth. Then carrier doping was systematically controlled in a wide range from underdoping to overdoping by post annealing under various conditions. T{sub}c of the crystals was found to vary from 98 K (underdoped) to 108 K (overdoped) with T{sub}c = 110 K for optimally-doped. In the optimally-doped phase the electromagnetic anisotropy factor, γ{sup}2 of Bi2223 was smaller than that of Bi2212. Abrupt resistivity drop was observed under fields below the second peak field of the magnetization hysteresis loops, suggesting a first order phase transition of the flux line lattice. Magnetic phase diagram of Bi2223 single crystals for H∥C was found to be similar to that of Bi2212.