Tricritical Phenomena at the Cerium $\gamma \to \alpha$ Transition

TL;DR

This study investigates the Ce$_{0.9-x}$La$_x$Th$_{0.1}$ system's $ ext{γ} o ext{α}$ transition, revealing a tricritical point where the transition shifts from first-order to continuous, accompanied by evolving heavy Fermi-liquid behavior.

Contribution

It provides detailed experimental evidence of tricritical phenomena at the $ ext{γ} o ext{α}$ transition in cerium alloys with La doping, identifying the critical concentration and associated electronic changes.

Findings

Transition temperature decreases exponentially with La doping.

A tricritical point occurs near $x=0.14$, marking a change from first-order to continuous transition.

Heavy Fermi-liquid behavior develops at high doping levels.

Abstract

The $\gamma \to \alpha$ isostructural transition in the Ce$_{0.9-x}$La$_x$Th$_{0.1}$ system is measured as a function of La alloying using specific heat, magnetic susceptibility, resistivity, thermal expansivity/striction measurements. A line of discontinuous transitions, as indicated by the change in volume, decreases exponentially from 118 K to close to zero with increasing La doping and the transition changes from being first-order to continuous at a critical concentration $0.10 \leq x_c \leq 0.14$. At the tricritical point, the coefficient of the linear $T$ term in the specific heat $\gamma$ and the magnetic susceptibility start to increase rapidly near $x$ = 0.14 and gradually approaches large values at $x$=0.35 signifying that a heavy Fermi-liquid state evolves at large doping. Near $x_c$, the Wilson ratio, $R_W$, has a value of 3.0, signifying the presence of magnetic fluctuations. Also, the low-temperature resistivity shows that the character of the low-temperature Fermi-liquid is changing.