Narrow bands and magnetic properties of heavy fermions (abstract)

Abstract

Far infrared measurements performed at low temperature on the heavy fermions UPt3 and CeCu6 give us evidence that an appropriate model describing these materials must consider two narrow quasiparticle bands in the vicinity of the Fermi level separated by a gap, or a pseudogap, in the order of a few meV. The bandwidth obtained by point contact spectroscopy is also in the meV range. With such a model and with the experimentally obtained values for the bandwidth and the gap we tried to calculated the temperature dependence of the resistivity and of the γ value of the specific heat and we found a very good agreement with the experiments. We want now to apply the model to calculate the magnetic properties of the heavy fermions. We show that a Pauli susceptibility including the effects of a strongly energy dependent density of states can account for the temperature dependence of the susceptibility in these materials. For temperatures above about 50 K we find a Curie law and for lower temperatures we compute a weak maximum. Furthermore, the magnetic saturation of UPt3 in very large fields (35 T) can be explained in this context as a splitting of the quasiparticle band at the Fermi level in two completely separated spin polarized subbands.