Current-voltage relations of YBa_2Cu_3O_x thin films in high magnetic fields

摘要

The current-voltage (I-V) relations of YBa_2Cu_3O_x thin films were measured with current densities up to 2x10~6 A/cm~2, in high magnetic fields up to 40T, and in both of longitudinal and Hall geometry, using three different techniques. In a high dissipation region, the I-V relations are still nonlinear, and the free flux flow state was not observed. The I-V relations for the Hall voltage were measured down to 45K in 40T. The Hall conductivity is nearly constant in the region of high current densities. The second sign reversal of the Hall effect was searched for applying high current densities, but was not found at 1T.