MAGNETIC-SUSCEPTIBILITY OF HEAVY FERMIONS AND MIXED-VALENCE SYSTEMS

The electronic and magnetic properties of heavy fermions and mixed valence systems have been, in the recent past, described by the periodic Anderson model (PAM). In this paper the magnetic behaviour of the Anderson lattice is studied using the variational method, proposed recently. With this variational method, the variation is studied of average valence and spin susceptibility with temperature for different values of hybridization, different effective values of the f-level, and for finite as well as infinite interaction U. When the f-level lies deep below the Fermi level, the susceptibility diverges in most of the temperature region for infinite U, while for weak interaction the divergence is reduced to a small temperature region. When the f-level lies near the Fermi level, the susceptibility is finite at T = 0 K, increases linearly at low temperature and shows Curie-Weiss behaviour at higher temperatures.