SIGN CHANGE OF THE FLUX-FLOW HALL RESISTANCE IN HIGH-TC SUPERCONDUCTORS

We consider a contribution to the flux-flow Hall effect that arises from the existence of large thermomagnetic effects in the mixed state of the high-T(c) superconductors. From the measured values of the Seebeck and Nernst-Ettingshausen effects we find that this contribution is as large as the direct flux-flow contribution to the Hall effect, but has the opposite sign for a positive Seebeck coefficient. Therefore it leads to a sign change of the Hall resistance. A calculation of the temperature and field dependence of the Hall resistivity yields good agreement with the data.