Superconductivity and non-Fermi liquid behavior near antiferromagnetic quantum critical points in CeRh_1−xCo_xIn₅

Single crystals of CeRh_1−xCo_xIn₅ have been investigated by means of specific heat measurements at zero pressure and electrical resistivity measurements under nearly hydrostatic pressure up to 28 kbar. Specific heat measurements for samples of CeRh_1−xCo_xIn₅ with cobalt concentrations of x=0.65, 0.71, 0.77, 0.87, and 0.93 confirm the existence of antiferromagnetism for 0⩽x⩽0.7 and suggest the existence of a quantum critical point at x_c∼0.75. Entropy versus x isotherms below ∼5 K and the normalized residual resistivity ρ(0 K)∕ρ(290 K) versus x curve both display maxima near x_c∼0.75, suggesting further evidence for the existence and location of the quantum critical point. Electrical resistivity measurements under pressure for samples with x=0.1, 0.2, 0.4, and 0.6 reveal antiferromagnetism, pressure-induced superconductivity, and the coexistence of antiferromagnetism and superconductivity. Normalized residual resistivity ρ(0 K)∕ρ(290 K) versus pressure P curves and the evolution of the power-law exponent n favor the existence of quantum critical points at critical pressures P_c∼23 kbar, ∼21 kbar, and ∼7 kbar for samples with x=0.1, 0.2, and 0.4, respectively.