Composition Effect of Kondo Behavior in Au–Al–Ce Quasicrystalline Approximants

We have studied the magnetic and transport properties of Tsai-type quasicrystalline approximants, AuxAl84−xCe16 and AuyAl86−yCe14 by the measurements of magnetic susceptibility χ, specific heat Cp and electrical resistivity ρ. A Curie-Weiss behavior in χ for all compounds indicates the stable trivalent state of Ce ions in Au–Al–Ce. The effective magnetic moment increases with increasing the Au concentration whereas the Weiss temperature decreases. These behaviors suggest the Kondo effect in Au–Al–Ce suppresses with the increase of Au concentration. In Cp, all measured compounds show a broad peak due to the Kondo resonance at 0.8 K. In addition, Cp/T shows a peak below 0.6 K, which implies the existence of spin-glass transition. In all compounds, a pronounced −log T behavior due to Kondo effect are observed in ρ(T) below 10 K. Moreover, AuyAl86−yCe14 approximants are the first example displaying a precursor of coherent Kondo state at low temperatures because a broad maximum is observed in ρ(T) at 1.3 K.