Competition between the BCS superconductivity and ferromagnetic spin fluctuations in MgCNi${}_3$

Abstract

The low temperature specific heat of the superconductor MgCNi${}_3$ and a non-superconductor MgC${}_{0.85}$Ni${}_3$ is investigated in detail. An additional contribution is observed from the data of MgCNi${}_3$ but absent in MgC${}_{0.85}$Ni${}_3$, which is demonstrated to be insensitive to the applied magnetic field even up to 12 Tesla. A detailed discussion on its origin is then presented. By subtracting this additional contribution, the zero field specific heat of MgCNi${}_3$ can be well described by the BCS theory with the gap ratio ($\Delta /k_B{T}_c$) determined by the previous tunneling measurements. The conventional s-wave pairing state is further proved by the magnetic field dependence of the specific heat at low temperatures and the behavior of the upper critical field.

To appear in Physical Review B, 6 pages, 7 figures

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Cited by in corpus (5)

• S-wave superconductivity probed by measuring magnetic penetration depth and lower critical field of MgCNi${}_3$ single crystals
• Superconducting energy gap in MgCNi3 single crystals: Point-contact spectroscopy and specific-heat measurements
• A first-principles comparison of the electronic properties of MgC_{y}Ni_{3} and ZnC_{y}Ni_{3} alloys
• Vacancies, disorder-induced smearing of the electronic structure, and its implications for the superconductivity of anti-perovskite MgC${}_{0.93}$Ni${}_{2.85}$
• Specific Heat and Upper Critical Field of Sc5Ir4Si10 Superconductor