BCS-like superconductivity in MgCNi₃

The low-temperature specific heat C(T,H) of the superconductor MgCNi ₃ has been measured in detail. ΔC/γ _n T _c = 1.97 is estimated from the anomaly at T _c . At low temperatures, the electronic contribution in the superconducting state follows C _es /γ _n T _c ≈ 7.96 exp(-1.46T _c /T). The magnetic-field dependence of γ(H) is found to be linear with respect to H. T _c estimated from the McMillan formula agrees well with the observed value. All the specific-heat data appear to be consistent with each other within the moderate-coupling BCS context. It is amazing that such a superconductor unstable to ferromagnetism behaves so conventionally. The Debye temperature Θ _D = 287 K and the normal state γ _n = 33.6 mJ/mol K ² are determined for the present sample.