Chapter 125 – Physical properties in layered transition-metal oxide crystals and anisotropic transport measurement

Publisher Summary This chapter applies two kinds of measurement methods to study the systematic transport property of both Bi 2-x Pb x Sr 2 Co 2 O y single crystals with various Pb content and Bi 2 Sr 2 CaCu 2 O y single crystals with various oxygen content. Anisotropic transport property measurement in strongly layered structure material is a challenge task. A key point is to overcome problems involving non-uniform current flow in the measuring process. Bi 2-x Pb x Sr 2 Co 2 O y is a misfit-layered compound, and Co ions in the conducting CoO 2 layer form a triangular lattice instead of a rectangular one in the conducting CuO 2 layer of high-T c cuprate oxides. The completely different anisotropic transport properties are observed in both Bi 2-x Pb x Sr 2 Co 2 O y and Bi 2 Sr 2 CaCu 2 O y crystals. For Bi 2-x Pb x Sr 2 Co 2 O y crystals, the evolution of pc behavior from semiconductive through crossover to metallic behavior is interpreted by a small-polaron model. As for high-T c cuprate, there is no consensus about the origin of semiconductor behavior of ρ c (T) so far. Therefore, more systematic investigation on related layered strongly correlated metals will help to clarify this problem.