Hall-effect measurements on superconducting and nonsuperconducting copper-oxide-based metals

The temperature dependence of the Hall effect was studied on single crystals of the layered copper oxide compounds ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$ (2:2:1:2) and ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CuO}}_6$ (2:2:0:1) with magnetic field perpendicular to and parallel to the CuO layers. dc-resistivity measurements indicated that the 2:2:1:2 samples have a superconducting transition temperature of 82–84 K; the 2:2:0:1 samples are metallic, but they did not show superconductivity down to 3.0 K. The Hall effect was found to be strongly anisotropic, and the interplane electronic transport is determined by electron hopping between the layers. For magnetic fields perpendicular to the layers, the superconducting compound shows a strongly-temperature-dependent anomalous increase in the Hall coefficient; the nonsuperconducting material has a much smaller, weakly-temperature-dependent Hall effect.