Kondo anomalies due to rare earth impurity ions

The experiments reviewed show that there is a phenomenological relationship between the Kondo-like anomalies in the physical properties of concentrated and dilute rare earth metallic systems. The anomalies can be viewed as originating from the hybridization of the localized 4f electron states and the extended states of the conduction band as a result of the unstable valence of certain rare earth ions. It has been demonstrated that Kondo-like behavior occurs in the physical properties of dilute rare earth metallic systems for the RE ions of samarium and europium. 5 figures