Intermediate valence and Kondo effect in Ce 1−xSc xAl 2

Abstract

Results of lattice parameter, thermal expansion, thermopower and magnetic susceptibility measurements are reported for Ce 1 − x Sc x Al 2, a system exhibiting a solubility gap over a wide composition range. Two isostructural phases are identified within the gap. For the Sc-rich systems, both phases contain intermediate valent (IV) Ce ions, whereas in the Ce-rich systems ( x < 0.5), a low-volume IV phase coexists with a high-volume phase containing Ce 3+ ions. The temperature-induced overall valence change of the IV ions amounts to 15–20%. A factor-of-three increase of the spinfluctuation temperature is found upon increasing the Sc concentration from x = 0.5 to 0.95. For the Ce-rich systems, we have discovered a hitherto not known “Kondo anomaly” in the temperature dependence of the thermal expansivity.