New approach to the theory of intermediate valence. II. Magnetic susceptibility and magnetic instabilities

Abstract

The previously introduced formalism to study the properties of some intermediate-valence solids is applied to calculate the magnetic susceptibility of various models and the instabilities of the paramagnetic state against ferromagnetism and antiferromagnetism. Our main results are: (i) A considerably enhanced susceptibility consisting of (a) a Hubbard-type Pauli contribution and (b) a Van-Vleck-type term due to higher configuration admixing. (ii) Instabilities against ferromagnetism and antiferromagnetism which are independent of the Van Vleck-type contribution and which differ somewhat from similar divergences found in the Hubbard model.