Microscopic investigation of electronic inhomogeneity induced by substitutions in a quantum critical metal CeCoIn5

Chemical substitutions are used commonly to tune a magnetic transition to zero temperature, but the resulting non-Fermi-liquid (NFL) behavior is nonuniversal. We have used nuclear quadrupole resonance to probe microscopically the response of a prototypical quantum critical metal CeCoIn5 to substitutions of small amounts of Sn and Cd for In. These substituents induce very different local electronic environments as observed by site-dependent spin lattice relaxation rates 1/T1 that influence the NFL behavior. The effects found here illustrate the need for care in interpreting NFL properties determined by macroscopic measurements.