On Some Ground State and Finite Temperature Properties of Mixed- Valence Compounds Induced by Next to Next-Nearest-Neighbor (NNNN) Hopping

Abstract

In the present study, effects of next to next-nearest-neighbor (NNNN) hopping of d-electrons in the crystal of mixed valence compounds has been discussed. Forconvenient theoretical calculation and computer simulation within exactdiagonalization method, a small cluster of eight lattice sites is considered here toinvestigate the valence transition through the study of the inter-site and on-site f-dcorrelation functions. Unusual magnetic behavior of mixed valence compounds hasalso been examined. Antiferromagnetic (AF) order has been developed in thecompounds of rare earth elements with the addition of NNNN hopping interactionwithin the extended Falicov-Kimball model. The extrapolation of the curves of thereciprocal susceptibility (-1) intercept at a negative temperature which confirms AForder in the system