Enhancement of Irreversibility Field in Carbon-substituted MgB2Single Crystals
Eiji Ohmichi, Takahiko Masui, Sergey Lee, Setsuko Tajima, Toshihito Osada
Journal of the Physical Society of Japan
We report the detailed study of the irreversibility field of single crystals of Mg(B_1-xC_x)_2 (x=0, 2, 3.5, 5 and 7 magnetic fields of up to 40 T. High sensitive torque measurements revealed that the is greatly enhanced by a factor of two (μ_0(0)≃33 T in x=5 the pristine owing to a reduction in the inplane coherence length. We also observed the temperature-dependent anisotropy in all the carbon contents. This fact strongly suggests that the two-gap superconductivity of is less influenced by a
... mall amount of carbon substitution. We discuss these results focusing on the impact of carrier doping and impurity scattering on two-gap superconductor.