Antiferromagnetic behavior in CeCo$_{9}$Ge$_{4}$

TL;DR

This study explores the magnetic properties of CeCo$_{9}$Ge$_{4}$, revealing antiferromagnetic order, Kondo interactions, and crystal field effects through comprehensive susceptibility and heat capacity measurements.

Contribution

It provides the first detailed investigation of the magnetic behavior and electronic interactions in CeCo$_{9}$Ge$_{4}$, highlighting coexistence of localized and itinerant magnetism.

Findings

CeCo$_{9}$Ge$_{4}$ orders antiferromagnetically at 12.5 K.

Presence of Kondo effect and crystal field splitting observed.

Co sublattice exhibits itinerant magnetic moments.

Abstract

We investigate the novel intermetallic ternary compounds \emph{R}Co$_{9}$Ge$_{4}$ with \emph{R} = La and Ce by means of $X$-ray diffraction, susceptibility and specific heat measurements. CeCo$_{9}$Ge$_{4}$ crystallizes in the space group ${I}$ 4/ ${mcm}$ and is characterized by the coexistence of two different magnetic sublattices. The Ce-based sublattice, with an effective moment close to the expected value for a Ce$^{3+}$-ion, exhibits a magnetically ordered ground state with $T_{\mathrm{N}}=12.5$ K. The Co-based sublattice, however, exhibits magnetic moments due to itinerant 3$d$ electrons. The magnetic specific heat contribution of the Ce-sublattice is discussed in terms of a resonance-level model implying the interplay between an antiferromagnetic phase transition and the Kondo-effect and an underlying Schottky-anomaly indicating a crystal field level scheme splitting into three twofold degenerated micro states ($\Delta_1 = 69$ K, $\Delta_2 = 133$ K).