Transport E-J characteristics in Bi-2223 tape under the influence of bending strain: Analysis by use of the percolation model

The influence of bending strain on the transport E-J characteristics in Bi-2223 Ag/AgMg-alloy sheathed tape is studied by using the percolation model. Magnetic field- and temperature-dependent E-J characteristics in the tape have been measured at various conditions of bending strain. As the bending radius is reduced, the apparent critical current in the tape is reduced mainly because of the reduction of geometrical cross-section area due to cracking. However, if we extract the local current density taking into account the cracking, it can be seen that the value of critical current density, J_c, is enlarged due to the bending strain in the remained region. Namely, the pinning strength in the remained region is enlarged as the bending strain is increased. It will be shown that the present method allows us to separate the variation of the connectivity and the pinning strength originated from the strain.