Two-fluid model of heavy fermion formation and SR knight shift measurements in UBe

Heffner, R. H.; MacLaughlin, D. E.*; Sonier, J. E.*; Fundley, M. F.*; Thompson, J. D.*

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e6 - e8, 2007/03

Recently phenomenological picture of the formation of the heavy femion state was put forward in terms of a two-component susceptibility, one component corresponding to non-interacting local moments and second, low-temperature component associated with onset of heavy fermation state (so-called "two-fluid" model). This phenomenology can be studied by measuring the local susceptibility via SR Knight shift measurements. Normally, the Knight shift is proposional to the bulk susceptibility. The onset of second component appears as a deviation in the linear relation. Previously we discovered a non-linear relation in UThBe, which was interpreted in terms of a temperature-dependent hyperfine field. Here we reexamine these data in terms of the two-fluid model. Our analysis shows that these date are consistent with the scaling law proposed. The SR data are discussed in terms of related changes in the resistivity and the NMR relaxation rates in these systems.