Determination of the relative influences of carbon doping and disorderon field and temperature dependent critical current density ofMgB2

Abstract

SiC was mixed with Mg and B and reacted by either a one-step in situ or two-step method at 650 or850 °C. By doing so, it was possible to determine the extent to which scattering viaC doping influences the magnitude of field dependent critical current density,Jc(H),compared to pinning via generation of microstructural disorder. The one-step reaction method leadsto Mg2Si formation and at the same time to more C doping ofMgB2 than the two-step method. Carbon increases both the irreversibility field,Hirr, and uppercritical field, Hc2 (T<28 K). However, for the temperatures (6 and 20 K) and fields (up to 7 T) studied, pinningrather than scattering overwhelmingly dominates the magnitude of the field dependentcritical current density.