Intermediate valence behavior in CeCo9Si4

TL;DR

This study investigates the intermediate valence behavior of the novel compound CeCo9Si4 through various measurements, revealing its unique paramagnetic state despite strong electronic correlations.

Contribution

It provides the first detailed characterization of CeCo9Si4, highlighting its intermediate valence and contrasting magnetic properties within the RCo9Si4 family.

Findings

CeCo9Si4 has smaller lattice constants indicating intermediate valence.

CeCo9Si4 remains paramagnetic even in high magnetic fields.

Electronic specific heat coefficient is comparable to ferromagnetic counterparts.

Abstract

The novel ternary compound CeCo$_9$Si$_4$ has been studied by means of specific heat, magnetisation, and transport measurements. Single crystal X-ray Rietveld refinements reveal a fully ordered distribution of Ce, Co and Si atoms with the tetragonal space group I4/mcm isostructural with other RCo9Si4. The smaller lattice constants of CeCo9Si4 in comparison with the trend established by other RCo9Si4 is indicative for intermediate valence of cerium. While RCo9Si4 with R= Pr, .. Tb, and Y show ferromagnetism and LaCo9Si4 is nearly ferromagnetic, CeCo9Si4 remains paramagnetic even in external fields as large as 40 T, though its electronic specific heat coefficient (g~190 mJ/molK^2) is of similar magnitude as that of metamagnetic LaCo9Si4 and weakly ferromagnetic YCo9Si4.