Mixed-Valent Ce Disrupts Magnetic Ordering in CeFe$_2$Ga$_8$

TL;DR

This study investigates CeFe$_2$Ga$_8$, revealing that mixed valency in Ce suppresses magnetic ordering and results in complex magnetic and electronic behaviors in this quasi-one-dimensional intermetallic compound.

Contribution

It provides a comprehensive analysis of CeFe$_2$Ga$_8$, showing how mixed valency influences magnetic properties and challenges previous reports of magnetic order in this material.

Findings

CeFe$_2$Ga$_8$ is a quasi-one-dimensional compound with mixed Ce valence.

The Fe sublattice is nonmagnetic, contrary to earlier reports.

No magnetic ordering observed down to low temperatures.

Abstract

Mixed valency in intermetallics with lanthanide cations is well established as a pathway to unusual charge transport, complex magnetism, and superconductivity. In this work, we report a comprehensive study of the structural, magnetic, electronic, and thermal properties of the mixed valent compound CeFe$_2$Ga$_8$. Powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS) characterize CeFe$_2$Ga$_8$ as a quasi-one-dimensional (Q1D) compound with mixed-valent Ce$^{3+}$ and Ce$^{4+}$ on a single crystallographic site. $^{57}$Fe M\"ossbauer spectroscopy indicates that the Fe sublattice is nonmagnetic, in direct contrast with recent reports of this compound. Low-temperature electrical resistivity and heat capacity measurements show no evidence of magnetic ordering, and a modest Sommerfeld coefficient ($\gamma$) of 22.7 mJ/mol$\cdot$K$^2$ make extensive Kondo hybridization unlikely. DC and AC magnetic susceptibility data suggest short-range magnetic order at $\sim$5.2 and 7.6 K with no frequency dependence, ruling out canonical spin-glass behavior in this compound. Additionally, the magnetic susceptibility data does not contain any broad features that are typically associated with an intermediate valence state in Ce, suggesting either high-temperature valence fluctuation or a different mechanism of mixed valency. This work demonstrates that mixed-valent Ce inhibits magnetic ordering in CeFe$_2$Ga$_8$ and provides a broader picture for how to analyze short-range spin interactions in Q1D intermetallics.