Competition between BCS superconductivity and ferromagnetic spin fluctuations inMgCNi3

L. Shan, Z. Y. Liu, Z. A. Ren, G. C. Che, H. H. Wen
2005 Physical Review B  
The low temperature specific heat of the superconductor MgCNi_3 and a non-superconductor MgC_0.85Ni_3 is investigated in detail. An additional contribution is observed from the data of MgCNi_3 but absent in MgC_0.85Ni_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
more » ... gap ratio (Δ/k_BT_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.
doi:10.1103/physrevb.71.144516 fatcat:ey2qtsr3qjbtphandrcf7abkjm