Carbon doping of superconducting magnesium diboride

By R. Ribeiro, S. Bud’ko, Cedomir Petrovic, P. Canfield. 2002

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Abstract We present details of synthesis optimization and physical properties of nearly single phase carbon doped MgB 2 with a nominal stoichiometry of Mg(B 0.8 C 0.2 ) 2 synthesized from magnesium and boron carbide (B 4 C) as starting materials. The superconducting transition temperature is ≈22 K (≈17 K lower than in pure MgB 2 ). The temperature dependence of the upper critical field is steeper than in pure MgB 2 with H c2 (10 K )≈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 MgB 2 even with such a heavily suppressed transition temperature. In addition, the anisotropy ratio of the upper critical field for T / T c ≈2/3 is γ ≈2. This value is distinct from 1 (isotropic) and also distinct from 6 (the value found for pure MgB 2 ).

Subfields: Condensed Matter Physics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/358339d43e1946bb89817358ae056359b64e11e1