Hall effect of the high-Tc superconducting oxides Bi-Ca-Sr-Cu-O and Tl2Ca2Ba2Cu3Ox

Abstract

The Hall coefficient $R_H$ has been measured in ceramic samples of the high-$T_c$ superconductors Bi-Ca-Sr-Cu-O and ${\mathrm{Tl}}_2{\mathrm{Ca}}_2{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_x$. The Bi compound is a mixture of the 2:1:2:2 and 2:2:2:3 phases whereas the Tl compound is single-phase 2:2:2:3. In both systems, $R_H$ is $T$ dependent and positive. A $\frac{1}{T}$ dependence is observed in the Bi compound. We discuss the significance of the low Hall number $\frac{1}{R_H}e$ (equivalent to ∼0.1 holes per Cu ion near $T_c$) implied by the large $R_H$ observed in both systems.