TEMPERATURE- AND FIELD-INDUCED VALENCE TRANSITION IN A MODEL FOR INTERMEDIATE VALENCE SYSTEMS

Abstract

Motivated by the experimental studies on the temperature- and field-induced valence transitions in Yb- and Eu-based rare earth compounds, a model calculation is performed. For this purpose, the periodic Anderson model, supplemented by the Falicov–Kimball term is chosen to describe the fluctuating valence systems. The model is solved first by decoupling the Falicov–Kimball term and then taking the intrasite Coulomb interaction strength to infinity. The resulting coupled equations for the spin dependent average occupations of the localized and itenerant states and the excitonic correlations have been solved self-consistently for different constellations of model parameters. The model calculations show that it is possible to induce valence transitions in the system by either varying the temperature or the field or both. The results obtained bear a rather striking similarity to the experimental observations not only in general but also in most of the details.