Coexistence of superconductivity and antiferromagnetism inCeRh1−xCoxIn5

Single-crystal specimens of ${\mathrm{CeRh}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}{\mathrm{In}}_{5}$ have been investigated by means of specific heat, electrical resistivity, and magnetic susceptibility measurements as a function of temperature. The measurements reveal the occurrence of superconductivity in compounds with $0.4l~xl~1.0$ with superconducting transition temperatures between $\ensuremath{\sim}1$ and 2 K and antiferromagnetic order in compounds with $0.2l~xl~0.6$ with N\'eel temperatures between $\ensuremath{\sim}3$ and 4 K. Superconductivity and antiferromagnetism appear to coexist for concentrations in the range $0.4l~xl~0.6.$ Specific-heat measurements indicate that the total entropy under the superconducting and antiferromagnetic transitions is comparable for the samples with $0l~xl~0.8,$ which implies that the same electrons are participating in the two phenomena. Measurements of the ac magnetic susceptibility revealed superconducting transitions in single-crystal specimens of ${\mathrm{CeRhIn}}_{5}$ at ${T}_{c}=0.09 \mathrm{K},$ but the superconductivity was suppressed when the samples were powdered.