A comparative study on field, temperature, and strain dependences of the critical current for doped and undoped MgB_2 wires based on the percolation model

摘要

Field, temperature, and strain dependences of the critical current for a SiC doped multifilamentary in situ MgB_2 wire have been studied. Measurement results were compared with that of the undoped wire, and the origin of the difference in the critical current is discussed. The critical current can be calculated with the percolation model considering the effect of anisotropy. The temperature dependence of the fitting parameters, the upper critical field along the ab-plane, and c-axis is compared with the dirty-limit two-gap theory. To assess the validity of the fitting parameters, resistive transition has been measured especially to extract the upper critical field directly. It is shown that even the resistive broadening can be well explained by a simple parallel path model using the fitting parameters obtained from the critical current analysis.