Self-consistent perturbation theory for dynamics of valence fluctuations

Dynamical property of an intermediate-valence Tm ion in a metallic matrix is investigated by the use of the self-consistent perturbation theory. Both of the fluctuating valence states in Tm have nonzero angular momentum in contrast to Ce and Yb systems. It is shown that the participation of two valence states in the magnetic susceptibility leads to peculiar magnetic properties such as enhanced Korringa-type magnetic relaxation and a systematic deviation from the Curie-Weiss law of the susceptibility. The susceptibility diverges in the zero-temperature limit. The dynamical susceptibility can be fitted by the Lorentzian lineshape very well for a wide frequency and temperature range. The single-particle excitation spectrum is also derived from which the resistivity is calculated. A logarithmic increase of the resistivity with decreasing temperature is found.