Kondo Anomalies due to Rare Earth Impurity Ions

Abstract

Rare earth (RE) ions are capable of producing “Kondo-like” anomalies in the physical properties of both concentrated and dilute RE metallic systems which are qualitatively similar. These temperature dependent anomalies scale with a characteristic temperature T0, above which the RE metallic system behaves magnetically and below which it behaves nonmagnetically. The physical properties in which Kondo-like anomalies are found include the electrical resistivity, magnetic susceptibility, thermoelectric power, specific heat, and, in systems where appropriate, superconducting properties such as the critical temperature Tc and the jump in specific heat which occurs at Tc. The anomalies can be viewed as originating from admixture of the localized 4f electron states with the extended states of the conduction band, which can be traced to the unstable valence of certain RE ions.