DOPING STATE AND TRANSPORT ANISOTROPY IN BI2212 SINGLE-CRYSTALS

Electrical resistivity was studied parallel to the ab-plane as well as along the c-axis of Bi2212 single crystals having both over-doped and under-doped states. The anisoropy within die ab-plane (perpendicular and parallel to the modulated b-axis directions) have been also systematically evaluated. The temperature dependence of rho(a), rho(b) and rho(c) was strongly dependent on the oxygen composition and the anisotropy Factors rho(c)/rho(a) and rho(c)/rho b showed a similar dependence; the more carrier doped crystals showed the smaller anisotropies in each case, while rho(a)/rho(b) showed an opposite dependence.