Influence of the electron-scattering mechanism on the critical current given by flux pinning at grain or twin boundary in high superconductors

(Received 5 February 1993, revised 2 November 1993, accepted 22 November 1993)

Abstract
The scattering caused by presence of grain or twin boundaries changes the local electronic properties of the material both in the normal state (mean free path, ...) and in the superconducting state (coherence length, ...). The consequences of electron-scattering mechanism on the critical current density given by ideal planar defects have been investigated for zero and large magnetic fields. For the case of large magnetic field, the critical current density dependences versus the magnetic field and the defect distance have been carried out. For the case of a 10 T applied magnetic field strength and for defect spacing largely smaller than 2 000 Å collective pinning is occurring, but for spacing largely larger than 2 000 Å it is the strong pinning. Finally the temperature behavior of the critical current density has been treated within the thermal flux creep model modified by the collective effects : i.e. the thermal activation energy is due to the contributions of the pinning well depth and of the bundle hopping energies.