UC San Diego

CeCoIn₅ has received a great deal of attention in recent years due to its exotic normal state behavior and possibly magnetically mediated superconductivity. In this work, we performed a two-part doping study of CeCoIn₅. First we investigated single crystals with dilute concentrations of several rare earths in the lanthanide series for Ce₀.₉₅R₀.₀₅CoIn₅. Second, in a more extensive substitution study, ytterbium was doped into the cerium sites for a full range of concentrations. For both cases, the synthesized compounds exhibited normal state NFL behavior, Kondo coherence, and magnetic anisotropy. In the rare earth study we found that the suppression of the superconducting transition Tc does not follow the conventional rate of suppression when a paramagnetic impurity is introduced into the system. In the ytterbium study a possible valence transition occurs for the Yb ion with increasing concentrations into the Ce sites. Single crystals of Ce₀.₉₅R₀.₀₅CoIn₅ and Ce₁-xRxCoIn₅ are investigated by means of x-ray powder diffraction, resistivity as function of temperature, and magnetic susceptibility