Magnetic field and current density dependence of the mixed-state Hall effect in Bi2Sr2CaCu2Ox

We report on measurements of the mixed-state Hall effect in Bi2Sr2CaCu2Ox t hin films in magnetic fields ranging from B = 60 mT to B = 1 T and current densities j up to 3 MA cm(-2). To reduce the problem of sample heating, we employed a pulsed current technique and developed a new heating correction procedure. We observe a double sign reversal of the Hall resistivity rho(yx ) in the mixed state, resulting in two peaks which both depend on B and j. The position of the sign changes only varies with B, but is found to be ind ependent of j. The Hall conductivity sigma(xy) turns positive again in the superconducting regime and dramatically increases towards lower temperature s and current densities, as the pinning is reduced by intense currents. (C) 1999 Elsevier Science B.V. All rights reserved.