We measured the low-temperature specific heat in magnetic fields up to 80 kOe, together with the magnetization for the heavy-fermion superconductor CeCoIn5 with the transition temperature Tc = 2.25 K. CeCoIn5 is a strong-coupling superconductor with a large jump in the specific heat ΔC/Cn(Tc) = 4.7. The heavy-fermion state is significantly formed below 1 K, reaching at least 1070 mJ/K2·mol in magnetic fields. This large electronic specific heat coefficient at 0.25 K is, however, reduced with increasing magnetic field, ranging from 1070 mJ/K2·mol at 50 kOe to 820 mJ/K2·mol at 80 kOe. The upper critical field Hc2 at O K is estimated to be 116 kOe for H ∥  and 49.5 kOe for H ∥ . The present anisotropy of Hc2 is well explained by the anisotropic effective mass, but the magnitude of Hc2 is reduced strongly by the paramagnetic effect for both field directions.
- CeCoIn specific heat
- Heavy fermion