Figure 1From: Carbon doping induced imperfections on MgB2 superconducting wire The critical current density and upper critical field of MgB2 wire. (a) Field dependence of the critical current density for the malic acid-doped sample at various temperatures. (b) Temperature dependence of the upper critical field extracted from the percolation model analysis. In (a), solid symbols are experimental data from the standard four-probe method using the electric field criterion of 1 μV/cm. Lines are calculated by the percolation model. In (b), lines are calculated by the two-band dirty-limit theory.Back to article page