Relationship between resistivity and specific heat in a canonical non-magnetic heavy fermion alloy system: UPt_5-xAu_x

TL;DR

This study investigates the relationship between resistivity and specific heat in UPt_5-xAu_x alloys, revealing how heavy-fermion behavior varies with composition and correlates with magnetic properties.

Contribution

It provides detailed measurements of resistivity and specific heat across a range of alloy compositions, highlighting the evolution of heavy-fermion characteristics and their relation to magnetic susceptibility.

Findings

Resistivity follows Fermi-liquid T^2 dependence at low temperatures.

The A/γ^2 ratio varies with composition, indicating a transition from transition-metal to heavy-fermion behavior.

The ratio correlates with the paramagnetic Curie-Weiss temperature.

Abstract

UPt_(5-x)Au_x alloys form in a single crystal structure, cubic AuBe_5-type, over a wide range of concentrations from x = 0 to at least x = 2.5. All investigated alloys, with an exception for x = 2.5, were non-magnetic. Their electronic specific heat coefficient $\gamma$ varies from about 60 (x = 2) to about 700 mJ/mol K^2 (x = 1). The electrical resistivity for all alloys has a Fermi-liquid-like temperature variation, \rho = \rho_o + AT^2, in the limit of T -> 0 K. The coefficient A is strongly enhanced in the heavy-fermion regime in comparison with normal and transition metals. It changes from about 0.01 (x = 0) to over 2 micro-ohm cm/K^2 (x = 1). A/\gamma^2, which has been postulated to have a universal value for heavy-fermions, varies from about 10^-6 (x = 0, 0.5) to 10^-5 micro-ohm cm (mol K/mJ)^2 (x > 1.1), thus from a value typical of transition metals to that found for some other heavy-fermion metals. This ratio is unaffected, or only weakly affected, by chemical or crystallographic disorder. It correlates with the paramagnetic Curie-Weiss temperature of the high temperature magnetic susceptibility.