Thermodynamic Investigation of Metamagnetic Transitions and Partial Disorder in the Quasi-Kagome Kondo Lattice CePdAl

TL;DR

This study investigates the low-temperature thermodynamic properties and magnetic phase diagram of CePdAl, revealing partial Kondo screening, metamagnetic transitions, and possible tri-critical point behavior in a quasi-Kagome lattice.

Contribution

It provides the first detailed thermodynamic analysis of the complex magnetic phases and transitions in CePdAl, highlighting partial Kondo screening and the nature of metamagnetic transitions.

Findings

Partial Kondo screening occurs on one-third of Ce sites.

Three distinct thermodynamic phases and crossover anomalies are identified.

Evidence suggests a tri-critical point near the phase boundary.

Abstract

Low-temperature ($T$) thermodynamic properties in magnetic fields ($B$) of the quasi-Kagome antiferromagnet CePdAl ($T_{\rm N}\sim$ 2.7 K) were studied by means of magnetization and specific-heat $C(T,B)$ measurements. The unusual magnetic phase diagram, including three thermodynamic phases I-III, and crossover anomalies, has been obtained. In low-field phase I, the existence of the partial Kondo screening state on the one-third Ce sites is supported from the thermodynamic point of view: (i) an appearance of the paramagnetic moment with one-third of the full moment around 3 T, and (ii) an occurrence of the entropy release $\sim$0.3$R$ln2 around the observed crossover. On the other hand, a strong enhancement of $C/T$ is found around the point, where $T_{\rm N}(B)$ meets the boundary of phase III, indicating the possible presence of a tri-critical point. Furthermore, it is suggested that the three metamagnetic transitions at $B_{{\rm m}i}$ ($i=$1,2,3) come from successive increments of the Ising-type magnetic moment along the $c$-axis. In high-field state above 20 T, the behavior of $f$ electron can be rather described by the crystal-electric-field model.