High-Field Superconductivity of Carbides

The high-magnetic-field properties of some refractory carbides were investigated at low temperatures. The upper critical fields for NbC, a solid solution of 40% NbC-60% TaC, and TaC are between 4.2 and 21.3 kG; MoC, Mo₅₆{C}₄₄$, and ${Mo}₆₀C₄₀+2% VC have upper critical fields between 80 and 120 kG; and Mo₃{Al}₂C has an upper critical field of 156 kG at 1.2^∘K.{Mo}₃Al₂C is the only known superconductor with the β-Mn crystal structure. From the available data the electronic specific-heat coefficient γ, the thermodynamic critical field Hc, the Ginzburg-Landau parameter κ, and the lower critical field Hc1 were estimated at the experimental temperatures.