Effects of high-oxygen-pressure annealing on transport properties for La1.89Ca1.11Cu2O6±δ single crystals

We have measured in-plane resistivities ρab(T), out-of-plane resistivities ρc(T), and Hall coefficients RH(T) of La1.89Ca1.11Cu2O6±δ single crystals as a function of temperature for various O2 annealing pressures. As-grown La1.89Ca1.11Cu2O6±δ single crystals which are semiconducting become superconducting if they are annealed under high oxygen pressures of more than 100 atm. In each metallic sample, the Hall angles reasonably fit Anderson's formula cotθH=αT2+C (α and C are constants and T is temperature). The phenomenological analysis using this relationship showed that the increase in Tc produced by the annealing mainly results from a reduction in the impurity scattering, while the metallic conduction itself is achieved by an increase in the carrier concentration.