Atypical thermodynamic behavior of Ce compounds in the vicinity of zero temperature Critical Points

TL;DR

This paper systematically analyzes thermodynamic properties of Ce compounds near quantum critical points, revealing atypical behaviors such as entropy reduction, non-monotonous volume changes, and different regimes of magnetic order as the system approaches zero temperature.

Contribution

It identifies and characterizes novel thermodynamic behaviors in Ce compounds near quantum critical points, including entropy anomalies and phase transition regimes, based on comprehensive experimental analysis.

Findings

Entropy reduction near critical composition x_{cr}

Non-monotonous volume variation V_0(x) at T=>0

Different regimes of entropy variation in the ordered phase

Abstract

A systematic analysis of thermodynamic properties performed on Ce-base exemplary compounds allows to identify different types of behaviors as the system approaches the quantum critical region. They are recognized in the respective magnetic phase boundaries (T_{N,C}(x)) as a change from the classical negative curvature to a linear composition ($x$) dependence, the occurrence of a critical point or the evanescence at finite temperature under pressure at finite temperature. In the first case, an anomalous reduction of the entropy S_m respect to the S_m = RLn2 value (expected for the usual Ce-magnetic doublet ground state) is observed around x_{cr}, and analyzed taking profit of detailed studies performed on CeIn_{3-x}Sn_x alloys. As expected from Maxwell relations, the volume variation V_0(x) at T=>0 also shows a non-monotonous behavior around x_{cr}. Different regimes in the entropy variation of the ordered phase (S_{MO}) are recognized. Only in the former case S_{MO}=> 0 continuously as T_{N,C}=>0, whereas in the second S_{MO}(x,B) remains constant till a first order transition occurs. In the third case, the degrees of freedom of the MO phase are progressively transferred to the heavy fermion component as indicated by the decreasing C_m(T_N) jump which vanishes at finite temperature.