Significant improvement of flux pinning and irreversibility field in nano-Carbon doped MgB2 superconductor

摘要

We report the synthesis and variation of superconductivity parameters such astransition temperature Tc, upper critical field Hc, critical current densityJc, irreversibility field Hirr and flux pinning parameter (Fp) for the MgB2-xCxsystem with nano-Carbon doping up to x=0.20. Carbon substitutes successfully onboron site and results in significant enhancement of Hirr and Jc(H).Resistivity measurements reveal a continuous decrease in Tc under zero appliedfield, while the same improves remarkably at higher fields with an increase innano-C content for MgB2-xCx system. The irreversibility field value (Hirr) is7.6 & 6.6 Tesla at 5 and 10K respectively for the pristine sample, which isenhanced to 13.4 and 11.0 Tesla for x = .08 sample at same temperatures.Compared to undoped sample, critical current density (Jc) for the x=0.08nano-Carbon doped sample is increased by a factor of 24 at 10K at 6 Teslafield.