THERMAL MEASUREMENTS OF THE MAGNETIC-FIELD INDUCED DISSIPATION IN YBA2CU3O7-DELTA AT LOW-TEMPERATURE

We have studied the magnetic field induced dissipation in YBa2Cu3O7-de lta for magnetic fields in the ranges (0-2 T) during virgin runs by di rectly measuring the heat produced. The magnetic field sweep rates are in the range (0-100 G/s). The measurements are performed at low tempe ratures, between 4.2 and 6.5 K. The dissipation induced by the electri c field produced by vortex movement has been modeled using the Bean cr itical state model. The dissipation was found to consist of two terms: the first one is due to the existence of the pinning force and the se cond is due to the viscous movement of the vortices. The fits of the e xperimental results, according to the theoretical form we have used fo r the dissipation j.E, led to the determination of the Bean field, in good agreement with the one obtained by magnetic measurements. We have also determined the effective resistivity corresponding to the viscou s dissipation at low temperature. The very small value obtained for th e latter is discussed.