ANGULAR-DEPENDENCE OF MAGNETORESISTIVITY AND HALL-EFFECT IN A YBA2CU3OX THIN-FILM

In this paper we present the magnetoresistivity and the Hall effect me asurements we have performed on a YBCO epitaxial film varying the angl e curly theta between the external magnetic field and the ab-planes. T he measurements are analyzed and discussed in terms of the scaling app roach proposed by Blatter and co-workers [13,20]. We concentrate our a ttention on an apparent failure of the scaling. This behaviour allows one to distinguish two regions where dissipation is dominated, respect ively, by thermal activation of the vortices pinned to extrinsic pinni ng centers and by the motion of free vortices and quasi-particles. The same identification of the dissipation regimes is obtained from the a nalysis of the Hall conductivity data. When the applied magnetic field direction is tilted towards the nb-planes, the structure of the vorti ces changes, fitting the layered structure of the lattice. The resisti vity in this region is analyzed in the light of the passage from tilte d to undulated vortex lattice. (C) 1997 Elsevier Science B.V.