Pd/Cu Site Interchange and Non-Fermi-Liquid Behavior inUCu4Pd

Abstract

to be published in Phys. Rev. Lett., LA-UR-98-3125) X-ray-absorption fine-structure measurements of the local structure in UCu4Pd are described which indicate a probable lattice-disorder origin for non-Fermi-liquid behavior in this material. Short Pd-Cu distances are observed, consistent with 24 ± 3% of the Pd atoms occupying nominally Cu sites. A "Kondo disorder" model, based on the effect on the local Kondo temperature TK of this interchange and some additional bond-length disorder, agrees quantitatively with previous experimental susceptibility data, and therefore also with specific heat and magnetic resonance experiments.

Lattice disorder and magnetism in f-electron intermetallics

“…The Ce-Rh/Ru fits indicate Θ cD =250 (20) The last example we present here is that of UCu 4 Pd. These results have been published previously [20][21][22]. To summarize, although the system was originally thought to be well ordered, a significant fraction (order of 25%) of the Pd atoms were found to reside on the nominally Cu sites.…”

Quantum critical fluctuations in the heavy fermion compound Ce(Ni0.935Pd0.065)2Ge2

“…The effect on the dynamic susceptibility will be that of an enhanced inhomogeneity rounding, which can explain the finite values of the correlation length and correlation time. It has also been shown [18][19][20] that such Kondo disorder can lead to the logarithmic temperature dependence of the specific heat coefficient and susceptibility and to a linear temperature dependence for the resistivity, as we observe in our sample for 2 T 10 K. In Montfrooij's view [16], the emergence of ordered magnetism must be understood in the context of percolation theory. In the simplest version of this idea, there will be two cerium environments.…”

Effect of annealing on glassy dynamics and non-Fermi liquid behavior in Pd

“…In UCu 4 Pd µSR relaxation [4,5] and inelastic neutron scattering [8,9] values of the scaling exponent γ are found to agree (γ ≈ 0.3), indicating a remarkable scaling of the spin dynamics scale over three orders of magnitude in frequency. EXAFS studies of UCu 4 Pd [10] showed that Cu-Pd site exchange was responsible for much of the observed disorder. Subsequently, thermodynamic and especially transport properties of UCu 4 Pd were found to depend strongly on annealing [11], which EXAFS measurements [12] showed decreased the degree of site-exchange disorder.…”