Mixed-Valent Ce Disrupts Magnetic Ordering in CeFe2Ga8

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 CeFe₂Ga₈. Powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS) characterize CeFe₂Ga₈ as a quasi-one-dimensional (Q1D) compound with mixed-valent Ce³⁺ and Ce⁴⁺ on a single crystallographic site. ⁵⁷Fe Mössbauer 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 (γ) of 22.7 mJ/molK² make extensive Kondo hybridization unlikely. DC and AC magnetic susceptibility data suggest short-range magnetic order at ~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 CeFe₂Ga₈ and provides a broader picture for how to analyze short-range spin interactions in Q1D intermetallics.