Thermal measurements of the magnetic field induced dissipation in YBa 2Cu 3O 7−δ at low temperature

Abstract

We have studied the magnetic field induced dissipation in YBa 2Cu 3O 7−δ for magnetic fields in the ranges (0–2 T) during virgin runs by directly measuring the heat produced. The magnetic field sweep rates are in the range (0–100 G/s). The measurements are performed at low temperatures, between 4.2 and 6.5 K. The dissipation induced by the electric field produced by vortex movement has been modeled using the Bean critical 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 second is due to the viscous movement of the vortices. The fits of the experimental results, according to the theoretical form we have used for 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 viscous dissipation at low temperature. The very small value obtained for the latter is discussed.