Anomalous Hall effect and vortex pinning in high-T-c superconductors

Pulsed high-current-density measurements of the Hall effect in the mixed st ate in several high-T-c superconductors allow for a systematical tuning of the balance between Lorentz and pinning forces on the vortices. The charact eristic temperatures for the single sign reversal in YBa2Cu3O7-delta and th ose for the double sign change of the Hall effect in optimally-doped Bi2Sr2 CaCu2Ox are independent of current density. This confirms that the observed sign changes of the vortex Hall effect are intrinsic properties and are no t evoked by vortex pinning. In contrast, underdoped Bi2Sr2CaCu2Ox does not exhibit a sign reversal of the Hall effect but a negative contribution to t he Hall conductivity can be detected when pinning is reduced in high-curren t densities. (C) 2001 Elsevier Science B.V. All rights reserved.