Field, temperature and strain dependence of the critical current for multi-filamentary MgB2 wire
We report detailed field, temperature and strain dependence of the critical current for a commercial multi-filamentary in-situ MgB2 wire. The field dependence of the critical current presented in the form of a Kramer plot was not linear near the irreversibility field for all temperatures measured. Instead, we found that the field dependence of the critical current can be well described by a recent model incorporating the Kramer model with a percolation theory proposed by Eisterer et al. [Phys. Rev. Lett. 90 (2003) 247002]. The temperature dependence of fitting parameters, the upper critical field along the ab-plane and c-axis is compared with that of the irreversibility field. It is further shown that the strain dependence of the critical current can be understood by the percolation model as related to a variation in the anisotropy factor of the upper critical field.