Site dependence of the Kondo scale in CePd1-xRhx due to Pd-Rh disorder

Abstract

We present measurements of the thermopower S(T) on CePd1-xRhx between 2 K and 300 K. For low Rh content, the system behaves as a ferromagnetic Kondo system with a Curie temperature TC of about 6 K, a Kondo scale smaller than TC, and an overall crystal electric field splitting of 210 K. As the Rh content increases TC is suppressed, while the average Kondo scale gets larger. Simultaneously, the presence of different Ce environments leads to a broad distribution of local Kondo scales ranging from very small values to above 50 K. As a consequence, large thermopower values are observed over an extended temperature range. Close to the critical concentration we find power-law dependencies of S/T vs T down to 2 K. For a Rh content of x=0.95 we may show explicitly that the thermopower contains contributions from Ce sites with different local energy scales.