Specific heat in high magnetic fields and non-Fermi-liquid behavior in CeMIn5 (M = Ir, Co) - art. no. 134524

The low-temperature specific heat, in magnetic fields to 32 T, and the magn etic susceptibility are reported on single crystals of the new heavy-fermio n superconductors CeMIn5, M=Ir and Co, as well as the new heavy-fermion ant iferromagnet CeRhIn5. The absence of a pronounced field dependence to the s pecific heat of the Ir and Co systems suggests that the large Sommerfeld co efficients of these compounds are due to correspondingly large effective el ectron masses. In addition, the indicated non-Fermi-liquid behavior previou sly suggested from the temperature dependence of the resistivity of CeIrIn5 has been confirmed in our measurements of the susceptibility and specific heat for this compound, as well as in the susceptibility and specific heat of CeCoIn5. The existence of superconductivity in these systems that appear s, based on their non-Fermi-liquid behavior, to develop near a quantum crit ical point is further support for this superconductivity being of unconvent ional nature.