Electron correlation effects in theoretical model of doped fullerides

Abstract

The general model for electronic subsystem of doped fullerides suitable for description of both semiconducting behavior and magnetic order onset with Coulomb correlation, intersite exchange interaction, correlated hopping of electrons and orbital degeneracy of energy levels all taken into account is formulated. Within the model, the magnetization and Curie temperature calculations allow extension of the model phase diagram and discussion of driving forces for ferromagnetic state stabilization observed in polymerized fullerenes and tetrakis(diethylamino)ethylene-fullerene. Curie temperature dependence on integer electron concentration at realistic values of the Coulomb correlation strength and Hund’s rule coupling, associated with orbital degeneracy of energy levels, is strongly asymmetrical with respect to half-filling. The competition of itinerant behavior enhanced by the external pressure application and localization due to the correlation effects is discussed.