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Carbon doping of superconducting magnesium diboride

R. A. Ribeiro·S. L. Bud'ko·C. Petrovic·P. C. Canfield
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Abstract

We present details of synthesis optimization and physical properties of nearly single phase carbon doped MgB2 with a nominal stoichiometry of Mg(B{0.8}C{0.2})2 synthesized from magnesium and boron carbide (B4C) as starting materials. The superconducting transition temperature is ~ 22 K (~ 17 K lower than in pure MgB2). The temperature dependence of the upper critical field is steeper than in pure MgB2 with Hc2(10K) ~ 9 T. Temperature dependent specific heat data taken in different applied magnetic fields suggest that the two-gap nature of superconductivity is still preserved for carbon doped MgB2 even with such a heavily suppressed transition temperature. In addition, the anisotropy ratio of the upper critical field for T/Tc ~ 2/3 is gamma ~ 2. This value is distinct from 1 (isotropic) and also distinct from 6 (the value found for pure MgB2).

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R. A. Ribeiro, S. L. Bud'ko, C. Petrovic, P. C. Canfield. 2002-10-23. Carbon doping of superconducting magnesium diboride. https://doi.org/10.1016/s0921-4534(02)02331-6

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