MIXED-STATE ODD HALL-EFFECT IN YBA2CU3O7-DELTA WITH UNIDIRECTIONAL TWINS

We have studied the mixed state Hall effect in YBa2Cu3O7-delta single crystals with unidirectional twins: rho(xy)=f(H). An analysis of the H all conductivity sigma(xy) in free flux flow regime reveals that sigma (xy) can be successfully described by two terms which are related to t he quasiparticle excitations and the motion of free vortices respectiv ely. We have discovered the strong twin dependence of the Hall conduct ivity sigma(xy) in the pinning (TAFF) regime and detected the sign rev erse of the Hall conductivity sigma(xy) at changing angle alpha (+45 d egrees-->45 degrees) between current and twin plane that indicated the presence of backflow of vortices. We have observed that sigma(xy) fen ds to -infinity while approaching the melting line. These results prov ide the evidence of strong planar pinning influence on the Hall conduc tivity.