Localised description of valence fluctuations.

Abstract

We set up a model for an intermedíate valence equivalent to the ‘atomic’ limit of the Anderson Hamiltonian. Detailed analysis of this model shows that most of the essential characteristics of valence fluctuators are already present in this crudely simplified Hamiltonian. We study the spin-spin and the 4f charge-charge correlation functions and show that it is possible to define a spin fluctuation frequency wit and a charge fluctuation frequency ω cf. ω ef and ω sf can differ considerably for some values of the parameters of the model. We calculate the magnetic susceptibility and the specific heat as functions of temperature and show how the results simulate the behaviour found in valence fluctuators.