Longitudinal and transverse magnetic susceptibilities of the intermediate valence compounds

Abstract

The authors calculate the magnetic susceptibility of the intermediate valence phenomena. They have used the periodic Anderson Hamiltonian (PAH) as the theoretical model, and the calculations were made using the two-particle Green function formalism. The PAH is decoupled using the alloy analogue approximation (AAA). The average one-particle Green functions are calculated using the coherent potential approximation (CPA), and with these functions they calculate the density of states. These results are compared with a pseudo-virtual-crystal approximation model. The magnetic susceptibility is expressed in terms of a two-particle Green function. This function, with the above model, can be reduced to two one-particle Green functions, and these can be averaged using the two-particle extension of the CPA formalism. The AAA breaks the spherical symmetry of the Hamiltonian, giving different results for the longitudinal and transverse terms. From symmetry considerations the authors find that the total susceptibility is the weighted average of the two terms. The susceptibility can be interpreted in terms of the Pauli, Van-Vleck-and Curie-Weiss-like terms. An extra term arises from the random character of the model. The results are compared with the experimental results.